Mayor Pete Buttigieg is leading some early state polls, but the South Bend, Indiana, mayor struggled under fire from his Democrat rivals on the debate stage on Thursday night.

The PBS/Politico Democrat presidential debate was mostly tame for the first hour, but Buttigieg’s response to attacks left him weakened on stage.

The three Democrat senators — Bernie Sanders, Elizabeth Warren, and Amy Klobuchar — teamed up against the South Bend mayor, attacking him for watered-down progressive proposals, a thin record of political achievement, and his coziness with billionaire fundraisers.

Warren brought up Buttigieg’s habit of fundraising with billionaires, targeting his recent “wine cave” fundraiser in Napa Valley, California, with billionaire Democrats.

“We made the decision many years ago that rich people in smoke-filled rooms would not pick the next president of the United States,” she said. “Billionaires in wine caves should not pick the next president of the United States.”

In response, Buttigieg fired back a series of canned lines practiced on the campaign trail with middling results.

“This is the problem with issuing purity tests you cannot yourself pass,” he said in an exchange with Warren, after pointing to her personal wealth.

Warren got the upper hand of the argument, particularly after Buttigieg suggested that funding from billionaires was essential to defeating President Donald Trump in 2020.

“These purity tests shrink the stakes of the most important election,” he argued, calling the war against Trump the “fight of our lives” that they could lose without billionaires.

Sanders quietly caved Buttigieg’s argument, as the party’s top grassroots fundraiser without funding from billionaires.

“Let me tell you how you win it: You have the largest voter turnout in the history of America,” he said. “And you don’t have the largest voter turnout unless you create energy and excitement.”

Sanders also mocked Buttigieg for failing to match former Vice President Joe Biden’s number of billionaire contributors: 39 to Biden’s 44.

“Pete, we look forward to you … I know you’re an energetic guy and a competitive guy to see if you can take on Joe on that issue,” Sanders said, prompting laughter in the crowd.

Buttigieg repeatedly raised his hand trying to respond to the attacks from the veteran senators, but he failed to ward off their attacks on his experience.

Klobuchar criticized the mayor for attacking the three senators’ experience in Washington, DC, noting that they achieved important victories for Democrats.

Buttigieg reacted by telling Klobuchar that they had “bigger fish to fry” than petty arguments about experience.

“Oh, I don’t think we have bigger fish to fry than picking a president of the United States,” Klobuchar shot back.

“You’re right,” Buttigieg admitted, pivoting to accuse Klobuchar of questioning his military service.

“I certainly respect your military experience. That’s not what this is about,” she replied. “This is about choosing a president.”

Klobuchar pointed out that Buttigieg failed at his attempt to win the chair of the Democratic National Committee race.

In response, Buttigieg relied on the narrative of coming out as a gay man prior to his reelection campaign and his military service.

“If you want to talk about the capacity to win, try putting together a coalition to bring you back to office with 80 percent of the vote as a gay dude in Mike Pence’s Indiana,” he boasted.

After coming out as gay, Buttigieg was reelected as mayor of South Bend with only 8,500 votes in his reelection campaign in a primarily Democrat city with a population of roughly 100,000 people.

Klobuchar pointed out that Buttigieg actually lost his statewide race for treasurer in Indiana, earning only 40 percent of the vote.

“Mayor, if you had won in Indiana, that would be one thing,” she said. “You tried and you lost by 20 points. I’m sorry. That’s just the math.”