Andrew Yang, Pete Buttigieg, and Amy Klobuchar won Thursday's Democratic presidential debate

• Seven of the 2020 Democratic presidential candidates took the stage in Los Angeles on Thursday night for the sixth round of presidential debates.
• South Bend Mayor Pete Buttigieg, Sen. Amy Klobuchar, and entrepreneur Andrew Yang emerged as the biggest winners of the night.
• Sen. Bernie Sanders didn't fare as well during the debate, fumbling a question about the lack of racial diversity in the 2020 race.
• Visit Business Insider's homepage for more stories.

Seven of the 2020 Democratic presidential candidates took the stage in Los Angeles on Thursday night for the sixth round of presidential debates.

South Bend Mayor Pete Buttigieg went on the attack a few times on Thursday night - largely targeting fellow frontrunner Sen. Elizabeth Warren.

In one of the most heated exchanges of the night, the Massachusetts lawmaker criticized Buttigieg for welcoming big money into his campaign and holding private fundraisers with wealthy donors.

"Billionaires in wine caves should not pick the next president of the United States, Mr. Mayor," Warren said, referring to a recent fundraiser Buttigieg held in Napa Valley, California.

Buttigieg shot back that Warren transferred millions of dollars she'd raised for her Senate campaigns, which were not restricted to small-dollar donors, to her presidential campaign. He argued that Warren's campaign finance rules would handicap Democratic candidates in an race in which their Republican opponent is raising record sums.

"This is the problem with issuing purity tests you cannot yourself pass," he said.

The two also clashed over whether public colleges should be tuition-free for all Americans - something Warren has proposed.

"I very much agree with Senator Warren on raising more tax revenue from millionaires and billionaires," Buttigieg said. "I just don't agree on the part about spending it on millionaires and billionaires when it comes to their college tuition."

One battle Buttigieg seemed to lose was against Sen. Amy Klobuchar, another winner of Thursday's debate.

In a back-and-forth about experience, Klobuchar accused the 37-year-old mayor of not valuing the experience she and other lawmakers have.

"So while you can dismiss committee hearings, I think this experience works," Klobuchar said. "And I have not denigrated your experience as a local official. I have been one. I think you should respect our experience."

The Minnesota senator also took a swipe at Buttigieg's electoral record in the Midwest, noting that the mayor lost a statewide race in Indiana by 20 points.

Klobuchar repeatedly interjected as other candidates sparred to make the case for her "bold" but "practical" progressive agenda.

Entrepreneur Andrew Yang also had a strong night, delivering well-received answers on questions concerning the lack of diversity in the presidential field to the protests in Hong Kong.

Yang was the only non-white candidate on stage on Thursday and was asked what message he thought the lack of candidate diversity sends to the country.

He started by complimenting his colleagues of color and then argued that the debate stage doesn't reflect America because many people of color don't have the necessary disposable income to donate to campaigns - a reference to both economic inequality and the role of money in politics. He then pivoted his answer to pitch his universal basic income proposal, which would send $1000 per month in taxpayer dollars to every American.

"I miss Kamala; I miss Cory, though I think Cory will be back," he said, referring to Sen. Kamala Harris, who dropped out of the race earlier this month, and Sen. Cory Booker, who didn't qualify for the December debate. "I guarantee if we had a freedom dividend of $1,000 a month, I would not be the only candidate of color on this stage tonight."

Yang also managed to hawk his book, "The War on Normal People," when asked what he'd gift the other candidates.

"I would love to give you each a copy of my book," he said to much laughter from the audience. "If you like data, this book is for you."

Sen. Bernie Sanders didn't fare as well during the debate. Early on in the evening he fumbled a question about the lack of racial diversity in the 2020 race. Instead of addressing the question head-on, Sanders pivoted to climate change and economic inequality.

Moderator Amna Nawaz, a PBS NewsHour reporter, interjected, "Senator, with all respect, this question is about race. Can you answer the question as it was asked?"

The audience laughed, creating an embarassing moment for Sanders

At another point, after the moderator mentioned remarks former President Barack Obama made recently about the lack of women in leadership and the tendency of older men to stand in the way, Sanders responded to the moderator's mention of his age by awkwardly joking about his race.

"And I'm white, as well!" he shouted, to a muted response from the audience.