Last week, Warren and Democratic activists successfully pressured Buttigieg into opening his private fundraisers to the press, and she trained her fire on him for one of his most recent locations: a wine cave in Napa Valley, California, including a Swarovski crystal-studded chandelier.

Buttigieg "just recently had a fundraiser that was held in a wine cave full of crystals and served $900 a bottle wine — think about who comes to that," Warren said. "Billionaires in wine caves should not pick the next president of the United States."

Warren, who has sworn off high-dollar fundraisers in her campaign, continued: "We can’t have people who can put down $5,000 for a check drown out the voices of everyone else."

Bernie Sanders and Andrew Yang jumped in, too, with Yang saying his universal basic income proposal would get more women to run for office “because they don't have to go shake the money tree in the wine cave.”

But Buttigieg zeroed in again on Warren, arguing that she's naive to write off a source of financial support against an extremely well-heeled incumbent president.

He pointed out that Warren attended high-dollar fundraisers when she ran for Senate in Massachusetts. She transferred $10 million she raised during that time to her 2020 account — much of which, Buttigieg pointed out, she raked in from the same big donors she's castigating now.

"Did it corrupt you, senator? Of course not," Buttigieg said of Warren's fundraisers during her Senate tenure. "So to denounce the same kind of fundraising guidelines that President Obama went by, that Speaker Pelosi goes by, that you yourself went by until not long ago to build the Democratic Party and build a campaign ready for the fight of our lives — these purity tests shrink the stakes of the most important election."

“This is the problem with issuing purity tests you cannot yourself pass," Buttigieg added. "If I pledge never to be in the company of a progressive Democratic donor, I couldn't be up here. Senator, your net worth is 100 times mine. Suppose you went home and felt the holiday spirit — I know this isn't likely, but stay with me — and decided to go on pete.com and gave the maximum, would that pollute my campaign because it came from a wealthy person? No. I would be glad to have that support. We need the support of everybody who is invested to help beat Donald Trump."

"I do not sell access to my time," Warren responded.

"Since when, senator?" Buttigieg interjected.

Warren didn't directly answer Buttigieg's assertion she was a latecomer to the cause, the implication being that she came around in a last-ditch effort to revive a flailing campaign. Instead, she reiterated her message.

"I said to anyone, if you want to donate to me, that's fine," she said. "But don't come around later expecting to be named ambassadors because that's what goes on in these high-dollar fundraisers. I said no and I asked everybody on this stage to join me. This ought to be an easy step."

One other candidate, Amy Klobuchar, took full advantage of the scrum. "I did not come here to listen to this argument," the underdog candidate from Minnesota said, in one of several strong moments for her in the debate. "I came here to make a case for progress. And I have never even been to a wine cave."