Here are some of the night's biggest moments.

Sanders, the millionaire socialist

A new NBC News/Wall Street Journal poll showed that two-thirds of voters are uncomfortable with a socialist candidate for president, which could be a problem for Sanders. But when asked about it, Sanders pointed out that he was leading in that very poll.

“Let's talk about democratic socialism," Sanders said, adding: "We are living in many ways in a socialist society right now. The problem is, as Dr. Martin Luther King reminded us, 'We have socialism for the very rich, rugged individualism for the poor.”

Applause rang out.

“When Donald Trump gets $800 million in tax breaks and subsidies to build luxury condominiums, that's socialism for the rich,” Sanders said. “We have to subsidize Walmart’s workers on Medicaid and food stamps because the wealthiest family in America pays starvation wages. That's socialism for the rich. I believe in Democratic socialism for working people. Not billionaires. Health care for all. Educational opportunity for all.”

Bloomberg quipped: “What a wonderful country we have. The best-known socialist in the company happens to be a millionaire with three houses. What did I miss here?”

Sanders: “You missed that I work in Washington.”

Bloomberg then cut in: “That's the first problem.”

Sanders continued, saying he has a home in Burlington, Vt. “I do have a summer cabin. Forgive me for that. Where is your home?”

“New York City, thank you very much,” Bloomberg responded. “And I pay all my taxes. And I'm happy to do it because I get something for it.”

Bloomberg appears to step in it on women and NDAs

One debate moment can cause a candidate to slip badly, and Bloomberg’s refusal to release women from non-disclosure agreements struck with his company marked a low point for his nascent candidacy.

“I have no tolerance for the kind of behavior the #MeToo movement has exposed. Anybody that does anything wrong in our company, we investigate it, and if it's appropriate, they're gone that day,” Bloomberg said when asked about complaints women have made against him over the years. Bloomberg pointed out that his company was rated as the second-best place in America to work.

That’s when Warren moved in for the kill: “I hope you heard his defense was: 'I've been nice to some women.' That just doesn't cut it."

She added: "What we need to know is exactly what's lurking out there. He has gotten some number of women — dozens, who knows? — to sign nondisclosure agreements both for sexual harassment and for gender discrimination in the workplace. So, Mr. Mayor, are you willing to release all of those women from those nondisclosure agreements? So we can hear their side of the story?”

Cheers and applause followed.

Bloomberg started to say, “We have a very few nondisclosure agreements,” when Warren interrupted him, asking, “How many is that?”

Bloomberg didn’t answer, but said none of the women “accuse me of doing anything other than, maybe, they didn't like a joke I told.”

The audience jeered.

“There’s agreements between two parties that wanted to keep it quiet. And that's up to them. They signed those agreements, and we'll live with it.”

Warren: “I want to be clear. Some is how many? And when you say they signed them, and they wanted them, if they wish now to speak out and tell their side of the story about what it is they alleged, that's now OK with you?"

She went on: "This is also a question about electability. We are not going to beat Donald Trump with a man who has who knows how many nondisclosure agreements and the drip, drip, drip of stories of women saying they have been harassed and discriminated against. That's not what we do as Democrats.”

Bloomberg responded finally: “I said we're not going to get — to end these agreements because they were made consensually, and they have every right to expect that they will stay private.”

More jeers followed.

Warren savages Bloomberg, the rest pile on

Elizabeth Warren welcomed Mike Bloomberg to the stage and whacked him rhetorically in a way so far unseen in the Democratic primary.

“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 to kick off the debate.

“Democrats are not going to win if we have a nominee who has a history of hiding his tax returns, of harassing women, and of supporting racist policies like redlining and stop and frisk,” she continued. “Look, I'll support whoever the Democratic nominee is, but understand this: Democrats take a huge risk if we just substitute one arrogant billionaire for another.”

Amy Klobuchar followed up, saying the Bloomberg campaign arrogantly said three moderate Democrats should just step out of the way to help him win the nomination and defeat President Donald Trump.

“I think we need something different than Donald Trump,” she said. “I don't think you look at Donald Trump and say, 'We need somebody richer in the White House.'”

After noting that an NBC poll showed he leads Trump by the widest margin of anyone in the Democratic field, Joe Biden piled on.

“The mayor says that he has a great record. The fact of the matter is, he has not managed his city very — very well when he was there. He didn't get a lot done,” Biden said. “He has stop and frisk, throwing close to 5 million young black men up against a wall.”

Dems criticize Sanders for online behavior of his supporters

A question to Warren about whether behavior of some Sanders supporters would hurt unity in the general election sparked a pile-on to the self-described democratic socialist.

“I've said many times before, we are all responsible for our supporters and we need to step up,” Warren said. “That's what leadership is all about.”

Sanders responded to Warren, saying of the millions of Twitter followers, “99.9 percent of them are decent human beings, are working people, are people who believe in justice, compassion and love. And if there are a few people who make ugly remarks, who attack trade union leaders, I disown those people.” He then pivoted to harassment he said some of his campaign’s female and African American staffers had received.

Buttigieg jumped in soon after, prefacing that he did not believe Sanders was directing the online activity, but then saying, “I think you have to accept some responsibility and ask yourself what it is about your campaign, in particular, that seems to be motivating this behavior more than others.”

Serious as a heart attack

Sanders backed away from his pledge to provide full transparency after he had a heart attack late last year. When asked about it, Sanders made sure to pivot to how Bloomberg had a medical procedure as well.

“I think the one area maybe that Mayor Bloomberg and I shared, you have two stents as well,” Sanders said.

Bloomberg chimed in: “25 years ago.”

“Well, we both have two stents. It's a procedure that is done about a million times a year,” Sanders said, pointing out that numerous physicians have attested to his health. “Hey, follow me around the campaign —three, four, five events a day, see how you're doing compared to me.”

Buttigieg chimed in and said it wasn’t enough.

“First of all, let me say we're all delighted that you are in fighting shape,” Buttigieg said and then transitioned to how Sanders has not provided enough details about his health care plan’s costs.

Sanders was happy to fight on more solid ground concerning health care, and pointed out that “Yale epidemiologists in ‘Lancet’ — one of the leading publications in the world — what they said, my friends, is Medicare for All will save $450 billion a year.”

Buttigieg blasts Bloomberg, Sanders

Buttigieg ripped into Bloomberg and Sanders, noting that after Super Tuesday, “the two most polarizing figures on this stage” could be the only two candidates left competing for the nomination.

“Most Americans don’t see where they fit if they’ve gotta choose between a socialist who thinks that capitalism is the root of all evil and a billionaire who thinks that money oughta be the root of all power,” the former South Bend, Ind., mayor said.

He urged the party to “wake up” and nominate someone like him.

“Let’s put forward somebody who actually lives and who works in a middle-class neighborhood in an industrial Midwestern city. Let’s put forward somebody who’s actually a Democrat,” Buttigieg said, jabbing Sanders, an independent, and Bloomberg, a former Republican and independent. “We shouldn’t have to choose between one candidate who wants to burn this party down and another candidate who wants to buy this party out. We can do better.”

Warren takes aim at, well, everyone

Warren didn’t come to make friends at the debate and, in one paragraph, swiped at Buttigieg, Klobuchar and Sanders over health care.

“Mayor Buttigieg really has a slogan that was thought up by his consultants to paper over a thin version of a plan that would leave millions of people unable to afford their health care. It's not a plan, it's a Power Point,” she said. “And Amy's plan is even less. It's like a Post-it note: ‘insert plan here.’ Bernie has started very much — has a good start. But instead of expanding and bringing in more people to help, instead his campaign relentlessly attacks everyone who asks a question or tries to fill in details about how to actually make this work. And then his own advisers say, ‘Eh, probably won't happen anyway.'”

All three candidates who were criticized wanted to respond, starting with Buttigieg.

“I'm more of a Microsoft Word guy,” drawing laughs. “If you look at my plan, I don't know if there are any Power Points on it but you definitely find the document on PeteForAmerica.com.”

Then it was Klobuchar’s turn: “I must say, I take personal offense, since Post-it notes were invented in my state.”

More applause.

Bloomberg ducks question on stop and frisk

Asked what his recently leaked 2015 comments that minority neighborhoods are where all the crime is and that the way to get guns out of people’s hands is to throw them against a wall and frisk them says about how he views people of color and minority neighborhoods, Bloomberg opted instead to talk about stop and frisk, a policing policy that disproportionately affected male African Americans.

The former mayor said he was “embarrassed” by how the policy turned out but emphasized that he inherited it from his predecessor. “What happened, however, was it got out of control,” Bloomberg said.

Bloomberg added that he has spoken to black clergy, business people and kids who had been stopped “to try to learn.” “If we took off everybody that was wrong off this panel, everybody that was wrong on criminal justice at some time in their careers, there’d be nobody else up here,” he said.

Though Bloomberg said he has apologized, Warren said to “listen very closely to the apology.”

“The language he used is about stop and frisk. It’s about how it turned out,” she said. “Now this isn’t about how it turned out. This is about what it was designed to do to begin with.”

It targeted black and brown men from the beginning, Warren continued, challenging Bloomberg to “issue a real apology.”

“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 even street, shutting out the sounds of people telling you how your own policy was breaking their lives,” she said. “You need a different apology here, Mr. Mayor.”

Too much money for Turbo Tax

Bloomberg said he will release his tax returns — eventually.

“It just takes us a long time,” he said, explaining why he hasn’t released his returns before voting started earlier this month. “Fortunately, I make a lot of money, and we do business all around the world, and we are preparing it. The number of pages will probably be in the thousands of pages. I can’t go to Turbo Tax.”

Bloomberg said his returns will include his investments and donations.

“They’ll be out in a few weeks, and that’s as fast as I can do it,” he added. “Remember, I only entered into this race 10 weeks ago. All my associates here have been at this for a couple of years.”

Warren urged Bloomberg to “pay overtime and get it done!”

“I wish it were that simple,” Bloomberg responded.