COUNCIL BLUFFS, Iowa – Massachusetts Sen. Elizabeth Warren, the first major Democratic candidate to announce a challenge to President Donald Trump, had only been in Iowa for a few hours when she laid down a marker with implications for every other Democrat who might run for president in 2020.

“We ought to be building a movement, and the way we do that is with lots of involvement from lots of people, not having billionaires buy these campaigns, whether we’re talking about super PACs or self-funding,” Warren told reporters after the first rally of her campaign, held in an event space attached to a bowling alley in this city on the Missouri River. “As Democrats, in a primary, we should lock arms and make sure this is the party of the people.”

Warren’s call to disavow super PACs and self-funding, along with a growing movement within the Democratic Party to reject donations from Wall Street and business interests, is set to reshape how Democratic candidates bring in the millions of dollars necessary to power their primary campaigns. And it’s a sign that the way dozens of 2020 candidates raise their cash will be just as important as how much they bring in and how they spend it.

It also represents a continuation of two trends from the 2018 elections. The first saw Democrats collect more than $1.2 billion in online, small-dollar donations via ActBlue. The second saw more than three-quarters of newly elected congressional Democrats pledge to say no to corporate PACs, which bundle donations from a business’ employees and funnel them to elected officials. The performance of candidates like former Rep. Beto O’Rourke (D-Texas) — who narrowly lost to GOP Sen. Ted Cruz — established the political potency of swearing off super and corporate PACs, although not without some pushback.

We’re hoping to create a domino effect. Any outliers will stick out like a sore thumb. Progressive Change Campaign Committee co-founder Adam Green

Warren won’t be the only candidate to discuss money in politics — expect almost every Democratic candidate to make it part of their stump speech, and for Montana Gov. Steve Bullock to place it at the center of his campaign if he runs — but Warren’s early entry has given her a chance to set the terms of debate. The Progressive Change Campaign Committee, which has long functioned as Warren’s unofficial political arm, has already begun to pressure other candidates to agree to the senator’s conditions.

“We’re hoping to create a domino effect,” said Adam Green, the co-founder of the PCCC. “Any outliers will stick out like a sore thumb.”

“This challenge is a proxy for cleaning up the Democratic brand, having it be associated with the people, not big money interests,” he said. “It incentivizes Democratic Party politicians to associate with regular people when they’re getting policy advice.”

End Citizens United, a political action committee that rallied congressional candidates to swear off corporate PAC donations, is hoping to convince Democratic candidates in 2020 to do the same. At an event in Washington, D.C., earlier this week, four freshly elected Democrats – Reps. Jason Crow (Colo.), Abigail Spanberger (Va.), Antonio Delegado (N.Y.) and Jared Golden (Maine) – said the argument helped them win over voters across the political spectrum.

“This should really be about powering their campaigns from the people,” said Tiffany Mueller, the president of End Citizens United, which hosted the event. “We think they should not have single candidate super PACs.”

Many Democrats who are potential presidential candidates in 2020 have already promised to stop accepting corporate PAC donations, including Sens. Cory Booker (N.J.), Kirsten Gillibrand (N.Y.), Kamala Harris (Calif.) and former Housing and Urban Development Secretary Julian Castro. But super PACs ― which can raise unlimited sums, provided they don’t coordinate with the candidate they’re supporting ― are more complicated: There’s nothing a campaign can do to stop allies from creating and funding one.

ASSOCIATED PRESS Massachusetts Sen. Elizabeth Warren made her first stop of the 2018 campaign in Council Bluffs, Iowa.

Fighting A ‘Caricature’

Warren’s stance is already having an impact. Political operatives preparing super PACs for candidates, and the millionaires and billionaires getting ready to pay for their own campaigns, are adjusting to the new environment, preparing arguments that their money is cleaner than it looks at first glance.

“I think people have a caricature in mind of what they’re criticizing,” said Steve Phillips, a Democratic donor and operative who is preparing a super PAC to back Booker’s bid for the presidency. Phillips said he envisioned thousands of donors contributing to a PAC to help organize voters of color, rather than a single billionaire keeping a candidate afloat with television ads, which was common in the GOP nomination fights of 2012 and 2016.

Phillips, who previously funded and organized super PACs for President Barack Obama in 2008 and Georgia gubernatorial candidate Stacey Abrams in 2018, said his group’s work to organize and register voters of colors in key states would help the progressive movement as a whole as much as aid Booker’s bid for the presidency.

“I expect, frankly, there are going to be thousands of people, many of them professionals of color, who are supportive of Cory and want to give him more than $2,700,” he said. “And we want to give them a vehicle, because we think he represents the best chance to reassemble the Obama coalition and bring back the White House.”

“I don’t think people are going to care nearly as much about where the money is from as where the money is spent,” he added.

Booker is highly unlikely to be the only candidate with a super PAC backing him. In December, The New York Times reported that allies of both Gillibrand and Harris were discussing creating super PACs.

Self-Funders Shrug It Off

ASSOCIATED PRESS Former Maryland Rep. John Delaney, the first Democratic candidate to announce a run against Trump, is using his personal fortune to pay for his campaign.

Warren’s challenge is even more direct for candidates who are funding their own campaigns. Although billionaire donor and hedge fund founder Tom Steyer announced he wouldn’t run for president on Wednesday, former Maryland Rep. John Delaney is already running, and former New York City Mayor Michael Bloomberg is widely seen as considering a bid. Both men have historically funded their own campaigns.

“We’re focused on running a campaign of ideas and would welcome a debate on the issues,” said John Davis, a senior adviser to Delaney, who has already loaned his campaign $3.5 million. “Also, we happen to believe voters and not politicians should decide which candidates to nominate.”

Bloomberg ― who spent $100 million or more on his mayoral races ― told reporters on Friday in Texas his wealth allowed him to make decisions without being beholden to donors, a common argument used by self-funders.

“I used only my own money so I didn’t have to ask anybody what they wanted in return for a contribution,” Bloomberg said, according to the Associated Press. “And, if I ran again, I would do the same thing. I think not having to adjust what you say and what you work on based on who financed your campaign is one of the things that the public really likes.”

The Small-Dollar Battle

Democrats have been arguing over how best to raise money since at least 2004, when campaign finance advocates attempted to get the candidates to agree on a spending limit. Howard Dean, who pioneered online fundraising, and John Kerry, who spent millions of his own cash, both tossed aside the pledge. In 2016, Sen. Bernie Sanders (I-Vt.) made denunciations of super PACs set up to back Hillary Clinton a centerpiece of his campaign.

Warren and then-Sen. Scott Brown (R-Mass.) reached an agreement, dubbed “The People’s Pledge,” during her 2012 race that essentially barred super PACs and other outside groups from spending in the contest. It’s unclear if Warren will propose a similar pledge for the presidential contest.

This challenge is a proxy for cleaning up the Democratic brand, having it be associated with the people, not big money interests. Adam Green

Her new call is somewhat self-serving. Warren is one of a select group of candidates or potential candidates — along with O’Rourke and Sanders — with a demonstrated ability to raise mountains of small-dollar cash from online donors. (Harris, Gillibrand and Ohio Sen. Sherrod Brown also have large donor lists, but without the track record of the former three candidates.)

There is some risk in relying on $5 and $10 internet donations: Although Warren and other candidates have found it easy to bring in money against Republicans, donors might not be as eager to give when Democrats are competing against other Democrats, some operatives warned.

“On their own, or one on one, a handful of candidates have the potential for incredible programs. But all against each other? In a crowded primary? No one knows if they’ll be able to raise such massive sums online,” said Greg Berlin, one of the founders of the Democratic digital firm Mothership Strategies. “Will donors give to multiple candidates? Will they pick a horse? Will they shift support multiple times?”

It is likely every candidate in the race will need to show at least some ability to bring in online donations. The Democratic National Committee has said eligibility for debates will be determined, in part, by “grassroots fundraising,” though the terms remain vague.

Still, some Democrats are worried about falling into a “purity battle where we don’t know where it ends up,” as Mueller, the End Citizens United president, put it. Almost every candidate in 2020 has taken cash from interest groups or PACs in the past and could open themselves up to charges of hypocrisy. Warren, for instance, has taken more than $1 million from union and ideological PACs over the course of her career. And her opponents will notice.

“It’s kind of amusing that Sen. Warren herself has been perfectly happy to take money from billionaires for her Senate campaign,” Phillips said.

Warren, meanwhile, shows no sign of letting up on her message. She mentioned it at every stop of her three-day sojourn across Iowa, and is expected to do the same when she campaigns in New Hampshire on Saturday. On Wednesday afternoon, her campaign sent out a list-building email on the topic. The headline?

“Every Democratic presidential candidate should agree on this.”