In the fall of 2018, Emily’s List had a dilemma. With congressional elections approaching and the Supreme Court confirmation battle over Judge Brett M. Kavanaugh underway, the Democratic women’s group was hosting a major fund-raising luncheon in New York. Among the scheduled headline speakers was Michael R. Bloomberg, the former mayor, who had donated nearly $6 million to Emily’s List over the years.

Days before the event, Mr. Bloomberg made blunt comments in an interview with The New York Times, expressing skepticism about the #MeToo movement and questioning sexual misconduct allegations against Charlie Rose, the disgraced news anchor. Senior Emily’s List officials seriously debated withdrawing Mr. Bloomberg’s invitation, according to three people familiar with the deliberations, who spoke on the condition of anonymity.

In the end, the group concluded it could not risk alienating Mr. Bloomberg. And when he addressed the luncheon on Sept. 24 — before an audience dotted with women clad in black, to show solidarity with Christine Blasey Ford, the woman who accused Judge Kavanaugh of sexual assault — Mr. Bloomberg demonstrated why.

“I will be putting more money into supporting women candidates this cycle than any individual ever has before,” he declared.

It was not an idle pledge: Mr. Bloomberg spent more than $100 million helping Democrats take control of the House of Representatives in the midterm elections. Of the 21 newly elected lawmakers he supported with his personal super PAC, all but six were women.

The decision by Emily’s List, to mute its misgivings and embrace Mr. Bloomberg as a mighty ally, foreshadowed the choice Mr. Bloomberg is now asking Democrats to make by anointing him their presidential nominee.

Michael R. Bloomberg speaking about gun violence at an event in December, days after announcing his presidential bid. Chet Strange for The New York Times

There are, after all, numerous dimensions to Mr. Bloomberg’s persona and record that give Democrats pause. A former Republican who joined the Democratic Party in 2018, Mr. Bloomberg has long mingled support for progressive causes with more conservative positions on law enforcement, business regulation and school choice. He has often given voice to views that liberals find troubling: Over the past week, Mr. Bloomberg’s campaign was on the defensive over past recordings that showed him linking the financial crisis to the end of discriminatory “redlining” practices in mortgage lending, and defending physically aggressive policing tactics as a deterrent against crime.

Yet in a primary campaign defined by Democrats’ hunger to defeat President Trump, Mr. Bloomberg is also offering himself up as a person singularly equipped to do so — a figure of unique standing and resources, with a powerful set of alliances and a fearsome political machine to draw on. His political rise has become a test of the impact one man’s wealth can have when he applies it to the political system with driving sophistication.

In less than three months as a candidate, Mr. Bloomberg has poured more than $400 million, and rapidly counting, into the campaign. But that figure pales in comparison with what he spent in prior years, positioning himself as a national leader with presidential ambitions.











This circle represents the $401 million that Mr. Bloomberg has spent on his 2020 campaign so far. Here’s how it compares with his political and philanthropic spending in the years leading up to his presidential campaign. Each of these circles represents a group or individual Mr. Bloomberg has given money to. Even Mr. Bloomberg’s disclosed philanthropic spending far outweighs his political spending. The bulk of that giving has been in the United States, but he has also given millions to organizations abroad. Some of his largest charitable giving has been for public health. Sources: Foundation Directory Online, nozasearch.com, Internal Revenue Service filings, Federal Election Commission, state disclosure databases, Center for Responsive Politics. | Note: Some of the biggest beneficiaries of his giving like Everytown for Gun Safety and Johns Hopkins University are not represented in full. Charitable data is from 2006 to 2018. Political data is from 1977 to 2019.

A Times examination of Mr. Bloomberg’s philanthropic and political spending in the years leading up to his presidential bid illustrates how he developed a national infrastructure of influence, image-making and unspoken suasion that has helped transform a former Republican mayor of New York City into a plausible contender for the Democratic nomination. If anything, his claim — and his support among anxious moderates — has grown stronger with the ascent of the “democratic socialist” Senator Bernie Sanders in early voting in Iowa and New Hampshire.

Since leaving City Hall at the end of 2013, Mr. Bloomberg has become the single most important political donor to the Democratic Party and its causes. His personal fortune, built on a financial information and news company, is estimated at over $60 billion. It fuels an advocacy network that has directed policy in dozens of states and cities; mobilized movements to take on gun violence and climate change; rewritten election laws and health regulations; and elected scores of politicians to offices as modest as the school board and as lofty as the Senate.

“Clearly, over the last several elections, there has not been a more important donor to the Democratic Party than Michael Bloomberg,” said former Gov. Terry McAuliffe of Virginia, who once chaired the Democratic National Committee. “He has led on guns. He has led on climate change. He has been involved in all these races.”

In all, Mr. Bloomberg has spent at least $10 billion on his charitable and political pursuits. The vast majority has gone to philanthropy, for causes that reflect his personal interests and passions, including $3.3 billion to his alma mater, Johns Hopkins University.

But The Times’s examination — based on a review of years of campaign and nonprofit tax filings, as well as interviews with more than 50 people who have benefited from his support — illustrates how deeply that philanthropy is entwined with Mr. Bloomberg’s political preoccupations. In fact, in 2019, the year he declared his presidential candidacy, Mr. Bloomberg’s charitable giving soared to $3.3 billion — more than in the previous five years combined. His campaign disclosed that total in response to inquiries by The Times, but the donations were not itemized and most of it does not fall under public disclosure requirements.

Mr. Bloomberg has probably spent more from his personal fortune on his presidential campaign than any politician in American history. And while there have been political megadonors like the casino tycoon Sheldon Adelson, philanthropic giants like Bill Gates and self-funded candidates like Ross Perot, never before has one presidential hopeful combined the influence and reach of all three.

Top Presidential Campaign Self-Funders Figures are adjusted for inflation. SELF- FUNDED AMOUNT YEAR PARTY SHARE OF CAMPAIGN CANDIDATE RESULT Michael R. Bloomberg 2020 Dem. Still running $401 million 100 % Tom Steyer 2020 Dem. Still running 96 243 Ross Perot 1992 Ind. Lost election 89 116 Donald J. Trump Won election 2016 Rep. 20 70 Steve Forbes 1996 Rep. Lost primary 88 61 Steve Forbes 2000 Rep. 80 Withdrew 57 Mitt Romney 2008 Rep. 39 Withdrew 53 Ross Perot Lost election 1996 Reform 21 27 Hillary Clinton 2008 Dem. Lost primary 5 16 Morry Taylor 1996 Rep. Lost primary 98 11 YEAR PARTY SELF-FUNDED AMOUNT SHARE OF TOTAL CAMPAIGN SPENDING CANDIDATE OUTCOME Michael R. Bloomberg $401 million 2020 Democrat Still running 100 % Tom Steyer 2020 Democrat Still running 243 96 Ross Perot Lost election 1992 Independent 116 89 Donald J. Trump 2016 Republican Won election 70 20 Steve Forbes Lost primary 1996 Republican 61 88 Steve Forbes 2000 Republican Withdrew 57 80 Mitt Romney 2008 Republican Withdrew 53 39 Ross Perot Lost election 1996 Reform 27 21 Hillary Clinton 2008 Democrat Lost primary 16 5 Morry Taylor 1996 Republican Lost primary 11 98 Note: Figures for Mr. Bloomberg and Mr. Steyer are based on amounts reported to the Federal Election Commission through Dec. 31, 2019, and Advertising Analytics data through Jan. 31, 2020. The share of their spending since Jan. 1 was estimated based on their public advertising and past spending patterns. · Sources: Center for Responsive Politics; Federal Election Commission; Advertising Analytics

It is not simply good will that Mr. Bloomberg has built. His political and philanthropic spending has also secured the allegiance or cooperation of powerful institutions and leaders within the Democratic Party who might take issue with parts of his record were they not so reliant on his largess.

In interviews with The Times, no one described being threatened or coerced by Mr. Bloomberg or his money. But many said his wealth was an inescapable consideration — a gravitational force powerful enough to make coercion unnecessary.

“They aren’t going to criticize him in his 2020 run because they don’t want to jeopardize receiving financial support from him in the future,” said Paul S. Ryan, vice president of policy and litigation at the good-government group Common Cause.

That chilling effect was apparent in 2015 to researchers at the Center for American Progress, a liberal policy group, when they turned in a report on anti-Muslim bias in the United States. Their draft included a chapter of more than 4,000 words about New York City police surveillance of Muslim communities; Mr. Bloomberg was mentioned by name eight times in the chapter, which was reviewed by The Times.

Mr. Bloomberg discussing policing in 2012, when he was mayor of New York. Justin Lane/European Pressphoto Agency

When the report was published a few weeks later, the chapter was gone. So was any mention of Mr. Bloomberg’s name.

Yasmine Taeb, an author of the report, said in an interview that the authors had been instructed to make drastic revisions or remove the chapter, and opted to do the latter rather than “whitewash the N.Y.P.D.’s wrongdoings.” She said she found it “disconcerting” to be asked to remove the chapter “because of how it was going to be perceived by Mayor Bloomberg.”

Other officials at the center disputed that account, arguing that there had been substantive reasons to revise or remove a section on police surveillance in New York from a report commissioned to examine right-wing groups targeting Muslims with explicit bigotry and conspiracy theories.

“Any and all edits to this report were done solely based on editorial and policy considerations,” said a spokeswoman, Daniella Gibbs Léger. The center, she added, had produced other content addressing policing in New York, including a “critical, hard-hitting video” on department policies under Mr. Bloomberg. A spokesman for Mr. Bloomberg said his team was unaware of any dispute at the think tank.

But at least one senior official wrote at the time that there would be a “strong reaction from Bloomberg world if we release the report as written,” according to an email reviewed by The Times. And three people with direct knowledge of the situation said Mr. Bloomberg was a factor.

Alienating him might not have been a cost-free proposition. When the report came out, he had already given the organization three grants worth nearly $1.5 million, and in 2017 he contributed $400,000 more, according to Ms. Léger and the center’s limited public disclosure of its donors.

Ms. Taeb, who left the center after the report was published, recently entered politics in Virginia. Now a member of the Democratic National Committee, she said she received a minute-long voice mail from Mr. Bloomberg in December.

“He said he was calling to introduce himself as a courtesy and wanted to sit down with me to tell me why he’s running and why he has a chance,” Ms. Taeb said, “and what he’s done with the Democratic Party.”

The Philanthropy Flood

Early in his second term as mayor, Mr. Bloomberg bought a six-story Beaux-Arts mansion on the Upper East Side of Manhattan and outfitted it as part charity, part governance laboratory. It has become the hub of his empire — headquarters of Bloomberg Philanthropies and until recently the seat of his political operation.

It was during his 12 years at City Hall that Mr. Bloomberg wrote the playbook for propping up allies and co-opting opponents with a mix of political and charitable giving. Even as he spent $268 million on his three campaigns and made $23 million in campaign contributions to others, his philanthropy gave away $2.8 billion, much of it to civic and cultural groups around New York.

Bloomberg’s Total Giving Below is a look at Mr. Bloomberg's corporate giving, political spending, foundation contributions and donations from his personal checkbook. Since 1997, he has donated nearly $9.5 billion, the Bloomberg campaign says. Sources: Bloomberg campaign; Federal Election Commission.

His philanthropy actually comprises three separate streams of money. But only one of them, the Bloomberg Family Foundation, is publicly accounted for. The Times’s examination found billions of dollars in donations, under the Bloomberg Philanthropies umbrella, that had not been previously disclosed or itemized — corporate giving by his company, Bloomberg L.P., and from his personal checkbook.

In all, by his own accounting, Mr. Bloomberg has given away nearly $9.5 billion since 1997, at an annual rate that has increased more than a hundredfold. In 2018, the year before he announced for president, he spent nearly $770 million. Last year’s $3.3 billion figure probably included a $1.8 billion donation to his alma mater, Johns Hopkins University, announced in November 2018. Even without it, his charitable giving roughly doubled.

His spending on electoral politics has also steadily increased, from about $11 million in 2013, his final year as mayor, to the more than $100 million during the 2018 midterms.

All of those funds flow not just from Bloomberg Philanthropies and Mr. Bloomberg’s super PAC, Independence USA, but through an array of advocacy groups that rely on him for donations in the tens of millions of dollars. A number of them are cornerstones of liberal politics, including the Sierra Club, one of the country’s most influential environmental groups, Planned Parenthood and Everytown for Gun Safety.

Bloomberg’s Money Flow Here’s a look at how Mr. Bloomberg’s money moves through organizations he is most closely connected to. MICHAEL R. BLOOMBERG Bloomberg L.P. Everytown for Gun Safety Global, private media company that he mostly owns Gun control lobbying and advocacy Individual donations and contributions Bloomberg Family Foundation Independence USA Super PAC Nonprofit organization POLITICAL SPENDING CHARITABLE CONTRIBUTIONS MICHAEL R. BLOOMBERG Bloomberg L.P. Everytown for Gun Safety Global, private media company that Mr. Bloomberg mostly owns Individual donations and contributions Gun control lobbying and advocacy Bloomberg Family Foundation Independence USA Super PAC Nonprofit organization POLITICAL SPENDING CHARITABLE CONTRIBUTIONS

The foundation, along with Mr. Bloomberg’s other entities, has become something of a talent stable for people he admires — public officials, business leaders and political strategists, among others. The foundation’s board looks almost like a shadow administration, including luminaries like former Senator Sam Nunn of Georgia and former Treasury Secretary Henry Paulson, and current or former executives from companies including American Express, Disney and Morgan Stanley.

Much of his charitable giving has been largely detached from politics, focusing on areas like the arts, higher education and global public health. Aides are quick to point out that maternal health programs in Tanzania and motorcycle helmet promotions in Vietnam are not exactly winning Mr. Bloomberg primary votes. The biggest beneficiary of his giving has been Johns Hopkins.

Yet his domestic philanthropy has also overlapped with his political agenda, tying him closely to powerful progressive interest groups and amassing reservoirs of gratitude, admiration and influence across the country.

His relationship with the Sierra Club is a case in point. While he was still mayor, Mr. Bloomberg began expressing a keen interest in climate change. The Sierra Club had been working for years to block the construction of coal-fired power plants but wanted to go on the offensive, forcing aging plants offline. In the summer of 2011, Mr. Bloomberg stood on a barge on the Potomac River with the group’s executive director, Michael Brune, to announce a $50 million gift to the group’s Beyond Coal initiative, a figure that has since grown to over $100 million.

Separately, Mr. Bloomberg has deployed his political apparatus to advance the same agenda. In 2015, he announced that he would spend more than $10 million running ads against state attorneys general who were litigating against the Obama administration’s efforts to regulate emissions. In 2018, he gave $5 million to the League of Conservation Voters, and partnered with the group to identify targets for his political giving, including elections for an obscure New Mexico panel that regulates energy utilities.

Howard Wolfson, a senior adviser to Mr. Bloomberg, said the former mayor tended to approach his large-scale causes by seeking out trusted partners — political leaders or organizations — and using various parts of his operation to support them.

“When we identify strong, effective leaders, our view is that we should invest in them,” he said.

That model of concentrating political and philanthropic spending has defined Mr. Bloomberg’s approach in other arenas.

A champion of charter schools, Mr. Bloomberg has used his wealth in numerous ways to sway education policy in Louisiana. As mayor, he began giving relatively small donations, several thousand dollars each, to candidates in Louisiana school board races. But that investment sharply increased after a former New York City deputy schools chancellor, John White, became Louisiana’s state education chief in 2012.

Mr. Bloomberg has made more than $5 million in political donations in the state, including $3.6 million to Empower Louisiana, an education-focused political committee chaired by a powerful Republican donor, and also backed Mitch Landrieu, the former Democratic mayor of New Orleans. Over the same period, Mr. Bloomberg gave nearly $15 million to the Baton Rouge Area Foundation to promote charter schools, and his foundation gave nearly $3 million to the City of New Orleans. Two former senior aides to Mr. Landrieu are now helping lead Mr. Bloomberg’s political strategy in the South and his national outreach to African-American voters.

A rally organized by Everytown for Gun Safety, an advocacy group Mr. Bloomberg founded. Anna Moneymaker/The New York Times

Some places have become points of convergence for numerous strands of Mr. Bloomberg’s agenda. In Washington State, he contributed more than $2 million to political committees focused on issues like gun control, carbon pricing, soda taxes and same-sex marriage. At the same time, he showered the City of Seattle with grant money for climate-related policy, and the Bloomberg-funded group Everytown for Gun Safety deployed lawyers there, first to help craft regulations and then to defend them in court.

The city’s mayor, Jenny Durkan, now sits on the steering committee of C40 Cities, an alliance of mayors confronting climate change. Mr. Bloomberg is the head of its board. Even in a city like her own, Ms. Durkan said, Mr. Bloomberg stands out.

“There’s a lot of wealth here, and I see a lot of people who are personally interested, to varying degrees,” she said. “I’ve never seen the Mike Bloomberg package before.”

Mr. Bloomberg’s giving to Johns Hopkins has also intersected with his political advocacy. In Maryland, where the university is among the state’s most prominent institutions, he spent more than a half-million dollars in 2014 seeking to elect a governor supportive of gun control. The Bloomberg name, politicians say, is well known throughout the state because of the institutions that carry it, most of all the Bloomberg School of Public Health at Johns Hopkins.

Dr. Joshua Sharfstein, a professor at the school, said the foundation kept in close touch to monitor the projects it funded, track their attention in the media and connect recipients of Mr. Bloomberg’s money with other people close to the former mayor.

“Sometimes they’ll call us and say, ‘There’s a mayor who is interested in this — can you talk to them?’” said Dr. Sharfstein, who directs the Bloomberg American Health Initiative, built on a $300 million donation from Mr. Bloomberg.

The range and reach of Mr. Bloomberg’s spending, experts say, cannot but play to his advantage in the presidential race.

“The fact that he can call in all these favors, all over the country — a normal person can’t do that,” said Adav Noti, chief of staff at the Campaign Legal Center. “A normal person will never be able to do that.”

Policy, the Bloomberg Way

On a national level, there is arguably no issue more closely associated with Mr. Bloomberg than gun control. Nor does any other issue better capture the tension between his preference for data-driven, incremental, top-down strategy and the surges of ambitious activism that have increasingly defined American politics.

It was a cause he embraced after winning re-election as mayor. On New Year’s Day 2006, Mr. Bloomberg declared in his inaugural address that he saw an urgent duty “to rid our streets of guns, and punish all those who possess and traffic in these instruments of death.”

That April, he convened a Gracie Mansion summit of 15 mayors from across the country, marking the beginning of Mayors Against Illegal Guns, which within a few short months included more than 100 civic leaders from 44 states.

Soon enough, Mr. Bloomberg ramped up his spending on politics beyond New York. Frustrated at the flow of firearms from Virginia, a state with lax gun laws, Mr. Bloomberg tried to buoy candidates in the state’s 2011 elections who shared his views.

Then, in 2013, he received a visitor in New York: Mr. McAuliffe, by then a candidate for governor of Virginia. He proposed to Mr. Bloomberg that he make the state a decade-long priority, with an eye toward empowering Democratic supporters of gun regulation.

“I walked out with a multimillion-dollar commitment that day,” Mr. McAuliffe recalled.

Mr. Bloomberg spent more than $3 million in Virginia that year through his super PAC, helping propel Mr. McAuliffe to the governorship and electing a Democratic attorney general supportive of gun control, according to the Virginia Public Access Project. He has plowed millions more into the state since then, culminating last fall with a takeover of the state legislature by Democrats who are now seeking to pass a series of tougher gun laws.

Then, after leaving office in December 2013, Mr. Bloomberg began expanding his advocacy operation. He founded a new group, Everytown for Gun Safety, which has since spent tens of millions of dollars pushing for gun control measures, with considerable success in swing states like Colorado and Nevada.

Incorporated as a nonprofit, Everytown does not need to disclose its donors or most of its expenditures, but officials there say Mr. Bloomberg typically provides roughly one-third of the group’s budget. While officials at Everytown said the group was ultimately independent, it is closely intertwined with Mr. Bloomberg’s political operation.

Everytown is managed directly by one of Mr. Bloomberg’s close lieutenants, John Feinblatt, a former New York deputy mayor whose wedding Mr. Bloomberg officiated in 2011. Numerous people connected to the group said it channeled Mr. Bloomberg’s priorities, including his strong preference for working with both parties.

The organization came into existence through an almost corporate-style merger: Mr. Bloomberg already had a gun control group, Mayors Against Illegal Guns, but he needed a grass-roots army to compete with the National Rifle Association. So it joined forces with an existing activist group, Moms Demand Action for Gun Sense in America, to form Everytown.

Moms Demand Action had sprung up on Facebook after the 2012 massacre at Sandy Hook Elementary School in Newtown, Conn. Volunteers organized into local chapters, held protests and lobbied for legislation. After a year of working long hours for no compensation, many volunteers were running on fumes and well aware their organization needed money.

Mr. Bloomberg promised to infuse the movement with $50 million, bringing his mayors’ group and Moms Demand Action under the Everytown umbrella. According to his spokesman, Mr. Bloomberg has underwritten the gun control movement with a total of $270 million since 2007. But with his backing came a stark shift in culture and a rigid new command structure, one that left some activists feeling they were pawns in matching red T-shirts.

People involved in the group described being forced to communicate exclusively in canned talking points. Kate Ranta, shot twice by her ex-husband in front of her young son, was a member of Everytown’s network of survivors. She was asked to address a rally on the steps of the Capitol, along with her son. Standing beside Nancy Pelosi, then the House minority leader, and Representative John Lewis, she found herself stumbling over the text she had been given.

“Someone from Everytown wrote my speech. It was pushing their legislative agenda versus my authentic voice,” Ms. Ranta said. “I couldn’t say ‘gun control.’ It was moderate messaging — ‘gun safety’ and ‘gun violence prevention.’”

Other members greatly appreciated the new direction from Everytown. “A structure began to be put into place, and we could avail ourselves of the data that was offered so we could speak more intelligently,” said June Rubin, a Moms Demand Action volunteer in New York. “So we’re focused and single-issue and highly recognizable and speaking with one voice, and it’s powerful.”

The policy agenda was to be focused on tightening background checks; more radical ideas like banning assault weapons were off the table. “There were people who were very, very troubled by that,” Ms. Rubin said. “I became very pragmatic.”

More confrontational tactics were also rejected. After the mass shooting last year at a Walmart in El Paso, Tex., other groups organized protests to pressure the retailer to change its policies. But Moms members were discouraged from attending and told not to show any affiliation if they did. One Moms official told volunteers in a closed Facebook group that doing otherwise could “undercut our relations with responsible gun owners whose support we need.”

“Our goal is always to get results, and sometimes that means playing the outside game and sometimes it requires playing the inside game and working with partners who have shown themselves to be amenable to change,” said Maxwell Young, chief of public affairs for Everytown. “We’ve found Walmart to be an ally on gun safety and an example of a leader always willing to engage in productive conversations.”

Mr. Bloomberg also insisted on a strategy of bipartisanship, frustrating activists who saw the Republican Party as unalterably opposed to their goals. In 2016, he spent nearly $12 million to re-elect Senator Pat Toomey of Pennsylvania, a Republican supportive of background checks but strongly conservative on nearly everything else.

Lisa Boswell, a former Moms volunteer who got involved after the Sandy Hook shooting, said activists in Pennsylvania were ignored. “While the ground volunteers were very much opposed to this idea, the decision was going to be made at a higher level, without taking those views into consideration,” she said.

Mr. Wolfson said that in the wake of Sandy Hook, Mr. Bloomberg felt strongly that Mr. Toomey’s support for background checks represented “an extremely important moment.” Mr. Bloomberg’s view, he said, was that “if you are asking someone to take a strong bipartisan stand in support of an absolute key priority, you want to be supportive of them.”

In 2018, even as Mr. Bloomberg was spending nine figures to defeat congressional Republicans, Everytown backed another Pennsylvania Republican, Rep. Brian Fitzpatrick, for re-election. A number of local volunteers, who said they had been assured that Everytown had no plans to support Mr. Fitzpatrick, quit to form their own gun control organization.

Former members of Moms Demand Action, who had been cut off from private Facebook groups and blocked by leadership on Twitter, were surprised when they received emails from Mike Bloomberg 2020. Then they learned his campaign had rented the group’s email list, for $3.2 million, two days before he announced his candidacy in November.

At least a half-dozen former Everytown and Moms Demand Action officials have joined the Bloomberg campaign, including senior political and legal strategists and the deputy director of the Survivors Network. Spokespersons for both the Bloomberg camp and Everytown said that they had put up a firewall in the campaign, and that there was no coordination between the two entities.

In his campaign, Mr. Bloomberg has proposed a gun control agenda that goes far beyond Everytown’s, including a ban on assault-style weapons and a national licensing system.

When Mr. Bloomberg spent roughly $10 million on a Super Bowl commercial this month, he chose to focus his 60-second spot entirely on gun control. The emotional ad featured Calandrian Simpson-Kemp, whose son had been shot and killed, and who previously appeared in videos for Everytown, wearing the distinctive red Moms Demand Action T-shirt.

Powerful Alliances

In the presidential race, Mr. Bloomberg has activated his sprawling network of allies to great effect — drawing on his foundation and its beneficiaries to build a campaign staff, and calling on politicians he has supported in the past for their endorsements.

It is that network, as much as the raw force of his campaign spending, that has propelled Mr. Bloomberg into contention in the Democratic race. He is not the only candidate spending hundreds of millions of dollars promoting himself: Tom Steyer, a billionaire former hedge fund investor, has spent at least $243 million of his fortune on the race but has struggled to win support.

Mr. Bloomberg’s trajectory has been different. He has climbed to the top rank of contenders, even catching up to former Vice President Joseph R. Biden Jr. in some national polls.

Since the start of his campaign, more than 50 employees of Bloomberg Philanthropies have moved across town to his Times Square campaign headquarters as paid staff members, including the foundation’s chief executive, Patricia E. Harris, a former New York deputy mayor, and James Anderson, previously the foundation’s head of government innovation.

Overnight, Ms. Harris and Mr. Anderson went from providing cities around the country with grants to contacting mayors for support. Dozens of current and former mayors have since endorsed Mr. Bloomberg, including leaders from major cities like Houston, Memphis, Tampa and Washington.

Two prominent Democratic leaders with direct ties to the foundation quickly renounced their support for Mr. Biden after Mr. Bloomberg joined the race. Former Mayor Michael A. Nutter of Philadelphia, a fellow attached to Mr. Bloomberg’s What Works Cities initiative, became a paid adviser to the campaign. Manny Diaz, the former mayor of Miami and a paid board member at Bloomberg Philanthropies, defected from Mr. Biden to Mr. Bloomberg several weeks later.

Mr. Bloomberg speaking this month at the National Constitution Center in Philadelphia. Hannah Yoon for The New York Times

Mr. Bloomberg’s campaign commercials have featured his crusades against coal, tobacco companies and the N.R.A. And he has continued to dole out money to the party — giving $10 million to a super PAC supporting House Democrats, $5 million to a voting-rights group led by Stacey Abrams, and hundreds of thousands of dollars to the Democratic National Committee as well as dozens of state parties. The D.N.C. recently revised its debate-qualification standard to make it possible for someone like Mr. Bloomberg, who does not accept political donations, to participate, drawing accusations of favoritism from other campaigns.

One of the first members of Congress to endorse Mr. Bloomberg was Representative Stephanie Murphy of Florida. Elected in 2016 as a champion of gun control, Ms. Murphy said she had worked closely with Everytown on legislation, and said Mr. Bloomberg had shown his political mettle by backing groups like the League of Conservation Voters and Planned Parenthood.

“All of these are organizations that supported and endorsed my campaign in ’16 and ’18,” Ms. Murphy said. “This is a guy who puts his money where his mouth is.”

Mr. Bloomberg has promised to do just that in the general election, spending aggressively to defeat Mr. Trump no matter who the nominee is. But advisers to Mr. Bloomberg acknowledged the scale and focus of his spending would differ, depending on whether he is the Democratic standard-bearer.

“If Mike Bloomberg is the nominee, he will ensure that the Democratic Party has the greatest funding in its history,” Mr. Wolfson said, describing a plan to guarantee “all 50 states have the resources that Democrats need to compete up and down the ballot.”

If Mr. Bloomberg is not nominated, Mr. Wolfson suggested a narrower focus. “If you’re trying to defeat Donald Trump and you’re not on the ballot, you’re going to focus on the battleground states,” he said.

There are places where Mr. Bloomberg’s past spending has left a less helpful mark for his campaign: Pennsylvania may be one of them, since some Democrats there still resent his past support for Mr. Toomey. Teacher unions view Mr. Bloomberg with distrust because of his donations to school-choice groups and his charter-friendly policies as mayor.

But in most places he has ventured as a candidate, Mr. Bloomberg’s many years of largess have helped earn him a warm reception.

During the week of the Iowa caucuses, he toured California with former Los Angeles Mayor Antonio Villaraigosa, for whom Mr. Bloomberg spent millions in a 2018 gubernatorial race, and San Jose Mayor Sam Liccardo, a beneficiary of Bloomberg foundation grants. He visited Providence, R.I., to be endorsed by Gov. Gina Raimondo, a moderate Democrat whose election Mr. Bloomberg aided in 2014. And he got an endorsement from Representative Mikie Sherrill of New Jersey, for whom Mr. Bloomberg’s super PAC spent more than $2 million in the last midterm elections.

Some of his biggest endorsements have come out of cities that have been focal points for his philanthropy. In the Bay Area, Mr. Bloomberg’s foundation has distributed dozens of grants to museums, dance companies and climate organizations, while his political donations have funded school board candidates and referendums to tax soda and ban e-cigarettes. San Francisco’s mayor, London Breed, endorsed Mr. Bloomberg last month, hailing his “ability to beat Trump.”

Mr. Wolfson said no promises had been made to Mr. Bloomberg’s endorsers about what they could expect from him down the line. “I haven’t had a single conversation with anyone where I suggested or implied any future support, nor did anyone ask for it,” he said.

So far, most lawmakers Mr. Bloomberg supported in 2018 have not endorsed him, but in interviews several acknowledged that his status as a patron of the party was weighing on their thinking. Sitting down with members of the centrist New Democrat Coalition on Capitol Hill last month, Mr. Bloomberg was greeted by a sequence of thank-yous from House members he backed in 2018, according to two lawmakers present.

Representative Scott Peters of California, a San Diego Democrat who endorsed Mr. Bloomberg, said he had been struck by the expressions of gratitude from his colleagues when Mr. Bloomberg visited the Hill.

“We know who he is — he’s a successful executive in business, he’s a successful executive in public life as mayor,” Mr. Peters said in an interview, adding, “We often say our checkbook is our values, and it was evident through his philanthropy that he shared my values on issues like gun safety and immigration and climate change.”