Democrats debated again on Wednesday in the run up to the Nevada caucuses, this time with the addition of a new player, billionaire and former New York City Mayor Michael Bloomberg, whose presence seemed to spark the most heated exchanges.

Though Bloomberg is not competing in Nevada, he has surged in recent polls that qualified him for his first debate of the 2020 Democratic primary. And he spent a lot of time on defense, taking hits from everyone on stage throughout the night.

Candidates talked over the moderators and each other, made sharp attacks and were asked to address a number of recent controversies, including Vermont Sen. Bernie Sanders' online supporters and Bloomberg's promised tax returns.

Here are some of the night's highlights:

Warren vs. Bloomberg, Sanders vs. Bloomberg ... Everybody vs. Bloomberg

The debate was not even 10 minutes in before the knives were out and candidates began piling on the former New York City mayor, who was a registered Republican as recently as 2018.

He was knocked for allegedly fostering a sexist and hostile work environment, his past support for the controversial "stop-and-frisk" policing strategy that impacted communities of color at disproportionate rates, and for funneling millions of his own money into ads. "Mayor Bloomberg, should you exist?" he was asked at one point.

“I actually welcomed Mayor Bloomberg to the stage," said Minnesota Sen. Amy Klobuchar. "I thought that he shouldn't be hiding behind his TV ads."

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Sanders said stop-and-frisk “went after the African American and Latino people in an outrageous way.” Later, former Vice President Joe Biden said, "The policy was abhorrent."

And Massachusetts Sen. Elizabeth Warren said Bloomberg was focusing his apology on "how it turned out," rather than what it was "designed to do."

“If you want to issue a real apology, then the apology has to start with the intent of the plan as it was put together and the willful ignorance day, by day, by day of admitting what was happening even as people protested in your own street," Warren said.

Bloomberg responded that he's "asked for forgiveness."

“But there is no great answer to a lot of problems and if we took off everybody that was wrong on this panel, everybody that was wrong on criminal justice at some time in the careers, nobody else would be up here," he said.

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Sanders also highlighted Bloomberg's Republican past, going after the businessman for endorsing President George W. Bush in 2004 and giving a small fortune to Republican causes for years.

Bloomberg switched to the GOP to run for mayor but later switched in the middle of his tenure to run as an independent. He became a Democrat in 2018 and started funding Democratic candidates and causes.

Sanders addresses alleged supporter attacks on union members

Sanders has been bombarded with questions about so-called "Bernie bros," online supporters who are said by critics to harass supporters of other campaigns, particularly women. Sanders has in the past offered a blanket condemnation of personal attacks, but maintained on Wednesday that the vast majority of his supporters are "decent human beings."

Former South Bend, Indiana, Mayor Pete Buttigieg claimed Sanders was “at war with (Nevada's) Culinary Union” after some of the senator's supporters reportedly threatened members for criticizing Sanders' "Medicare for All" plan.

Sanders responded to Buttigieg that his campaign has "more union support than you have ever dreamed of."

“If there are a few people who make ugly remarks, who attack union leaders, then I disown those people. They are not part of our movement,” he continued.

Buttigieg responded with a question: "What is it about your campaign in particular that seems to be motivating this behavior more than others?"

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Sanders said he doesn't think his movement has a disproportionate number of aggressive online supporters, explaining that "99.9% of them are decent human beings, are working people are people who believe in justice, compassion and love."

He said that this isn't an issue specific to his campaign, telling the other candidates to look at the attacks members of his campaign have faced, especially the ones directed at African American women.

Klobuchar's solution to quell sexism in online spaces? "We could nominate a woman."

The Culinary Workers Union represents 60,000 housekeepers, porters and bartenders working in Las Vegas casinos. At the top of the union’s presidential asks is to maintain the robust health care plans members have fought hard to negotiate and win.

The union announced last week that it would not endorse a candidate ahead of the caucuses this Saturday.

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Will Bloomberg withstand allegations of sexism?

Bloomberg was asked to address recent reports re-examining allegations of sexual harassment and a hostile work environment concerning him and his company.

"I'd like to talk about who we’re running against. A billionaire who calls women fat broads and horse-faced lesbians and no I’m not talking about Donald Trump, I’m talking about Mayor Bloomberg,” Warren said.

"I have no tolerance for the kind of behavior that the MeToo movement has exposed," Bloomberg responded, highlighting the number of women his company Bloomberg LP has in leadership positions.

"I hope you heard what his defense was: 'I’ve been nice to some women.' That just doesn't cut it," Warren said.

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Warren came after Bloomberg hard in a heated back-and-forth, asking him to commit to releasing women from their agreements and to announce how many women have made such agreements. Bloomberg maintained his argument that the NDAs were mutually agreed upon and shouldn't be lifted.

Bloomberg has in the past chalked up "bawdy" jokes he says he may have made as "the way I grew up." Numerous women are reported to be bound by nondisclosure agreements, keeping them from speaking publicly about allegations of sexism. And footage has resurfaced recently of Bloomberg speaking about transgender women as "some guy wearing a dress" as recently as 2019.

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Climate an urgent, moral issue to candidates

Sanders defended his Green New Deal as the only real solution to the “existential threat” posed by climate change.

“This is a moral issue, my friends,” he said.

The Green New Deal, criticized by some as a radical plan that would threaten the economy, has been a signature policy of Sanders and other progressives.

Most Democrats on the debate stage are not on board with the plan, though they support aggressive steps to reduce carbon emissions that lead to climate change, starting with the defeat of President Donald Trump.

Buttigieg again honed in on the need to nominate a candidate who is electable enough to take down the current president, and said Bloomberg and Sanders are the most "polarizing" figures on stage.

“Let’s be real. The deadline is not 2050. It’s not 2040. It’s not 2030. It’s 2020,” Buttigieg said. “Because if we don’t elect a president who actually believes in climate science now We will never meet any of the scientific or policy deadlines” to combat global warming.

"Let's make sure we're actually positioned to win," Buttigieg said.

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Capitalism or democratic socialism?

Bloomberg at one point essentially likened Sanders’ policies to communism and stood firmly behind capitalism.

"We're not going to throw out capitalism. We tried that. Other countries called that, it was called 'communism' and it just didn't work," Bloomberg said, to strong objection from Warren and Sanders.

“I’m not a communist, Mr. Bloomberg,” Sanders said, calling his remarks a “cheap shot.”

Bloomberg described himself as “lucky" to have become a success and said “a good chunk of it” goes to paying taxes. And as mayor, he said, “I raised taxes.”

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Sanders said the richest Americans are benefiting from a form of “democratic socialism” that provides millions in subsidies so they can consolidate wealth, while the poor are scraping by under a system of “rugged individualism” that shuts them out of economic opportunities.

Bloomberg said he worked hard to get what he has achieved, but Sanders said he owes some of that success to the workers at his company that helped build his fortune.

Bloomberg then slammed Sanders as a millionaire who owns three homes.

Contributing: John Fritze, Maureen Groppe, Savannah Behrmann and Ledyard King