The top six Democratic presidential candidates faced off in Las Vegas on Wednesday in the most combative debate of the election and days before the high-stakes caucuses in Nevada.

It was the first debate for Mike Bloomberg, and the former New York mayor’s rivals in the Democratic race for president immediately took aim – attacking him for his legacy on racist policing and reports of sexist comments and discrimination at his companies.

In the first minutes of the debate, the Vermont senator Bernie Sanders argued that Bloomberg’s legacy of stop-and-frisk made it impossible for him to broaden the Democratic party’s coalition and defeat Donald Trump.

Democratic debate: key takeaways from the bust-up in Las Vegas Read more

The Massachusetts senator Elizabeth Warren compared Bloomberg to Trump in her opening remarks: “Democrats take a huge risk if we just substitute one arrogant billionaire for another.”

From there, the attacks didn’t let up. Bloomberg gave ineffective responses to a series of stop-and-frisk questions, saying he was “embarrassed” by the tactic deployed in New York while he was mayor: “I’ve apologized. I’ve asked for forgiveness. We stopped too many people.”

He also claimed he “discovered” the city was conducting too many stops and that he reduced use of the policy. In reality, a court ordered the city to stop the practice, deeming it unconstitutional.

“You need a different apology,” Warren interjected.

Warren also targeted Bloomberg over non-disclosure agreements several women at his company have signed while settling lawsuits. She repeatedly urged him to disclose how many NDAs women had signed and to let the women speak freely about their experiences. Bloomberg demurred and ultimately refused to answer her direct questions, leading to boos from the crowd.

“In my company, lots and lots of women have big responsibilities,” Bloomberg responded.

“I hope you heard what his defense was: ‘I’ve been nice to some women,’” Warren shot back.

Wednesday’s debate at the Paris Theater in Vegas came one week after Sanders won the New Hampshire primary, setting the stage for a primary battle between the Vermont senator and the more moderate candidates. On the heels of a strong performance in the chaotic Iowa caucuses, the former South Bend mayor Pete Buttigieg came in a close second in New Hampshire, where the Minnesota senator Amy Klobuchar’s unexpected surge won her third place, and Warren and Joe Biden both experienced disappointing results.

Facebook Twitter Pinterest Bloomberg with Warren and Sanders. Photograph: Mario Tama/Getty Images

Bloomberg is not competing in Nevada, but he had been climbing in polls after spending more on ads than any candidate in US political history. He also sat out the Iowa and New Hampshire primaries and had mostly been making his case to voters through TV ads and scripted public events up until Wednesday’s debate.

Buttigieg and Klobuchar, the more centrist candidates from the midwest, were looking on Wednesday to broaden their coalitions in states like Nevada that are significantly more diverse than Iowa and New Hampshire.

Buttigieg went after Sanders and Bloomberg, claiming that they were “the two most polarizing figures on this stage” and that he had broader appeal.

But he clashed most fiercely with Klobuchar. Both midwestern candidates are competing in a crowded central lane, and tore each other down near the end of the debate. “You memorized a bunch of talking points,” Klobuchar said, telling the former mayor he has not been “in the arena”.

Buttigieg responded: “I’m used to senators telling mayors that senators are more important. You don’t have to be in Washington to matter.”

Earlier in the evening, Buttigieg had criticized Klobuchar, for forgetting the name of the president of Mexico, she responded: “Are you trying to say that I’m dumb? Are you mocking me here, Pete?”

Klobuchar, a former prosecutor, also faced difficult questions over her criminal justice record and her recent inability to name the president of Mexico.

Even though he is the frontrunner, Sanders avoided the brunt of attacks and benefited from the other candidates’ jabs at one another. Buttigieg was at one point asked to comment on an essay he wrote in 2000 praising the senator.

Following the debate, Warren’s surrogates brushed off questions as to why she had held her fire on Sanders. “It’s about showing who can bring together that coalition,” said Allison Stephens, a Democratic National Committee member from Nevada. Warren can bring “people who look like me and people who look like Nevada together”, she said, adding: “And I happen to be a millennial of color.”

Biden’s campaign had deployed additional staff to Nevada, hoping the caucus will deliver some sort of comeback after his poor performance in the first two states led to a significant drop in his national poll numbers. In the debate, the former vice-president went after Bloomberg with some energetic remarks but faced renewed questions about his record from Warren and other candidates and generally failed to break through.

Nevada is nearly 30% Latino and 10% black and has become increasingly Democratic in recent years. The state also has a strong record of supporting women in office and was the first in the country to have a majority-female legislature.

With the long-shot candidate Andrew Yang out of the race, the debate once again featured an all-white lineup.

Sam Levin (@SamTLevin) “This is the biggest election of our life time,” said Linda Gannon, a 49-year-old Vegas resident and English professor who showed up to #DemDebate hoping to get a seat to see Buttigieg, her top choice. “I’m a bit worried about him in Nevada, but I think he’s got a shot.” pic.twitter.com/vYU8tKsrdo

Before the start of Wednesday evening’s event, groups of Nevada voters had gathered inside the busy lobby of the Paris Theater. “This is the biggest election of our lifetime,” said Linda Gannon, a 49-year-old Vegas resident who showed up to the debate hoping to get a seat to see Buttigieg, her top choice. “I’m a bit worried about him in Nevada, but I think he’s got a shot. I feel confident any of the Democrats can beat Trump. We have to feel that way, and I will support any of them.”

Lorraine Oliver, a 68-year-old public health nurse in line to get into the debate, said she recently got a chance to meet Warren in person and was sold.

“She has such in-depth knowledge. But she’s not polling as well as I’d like. I need her to shoot up in the polls,” she said, adding: “I’m excited for an opportunity to get rid of Trump. He’s done enough to make people angry. We’re gonna fight back.”

Also on line were several Andrew Yang fans who said they were continuing to advocate for their favorite candidate, even though he has already suspended his campaign.

“It’s larger than him. It’s about his movement,” said Hannah Won, a 37-year-old arts advocate.