On Thursday, Democrats held their sixth presidential debate in Los Angeles and Sen. Elizabeth Warren sparked the biggest moment of the night when she attacked Mayor Pete Buttigieg for holding a large-donor fundraiser at a posh, Swarovski crystal–filled wine cave in California’s Napa Valley.

The clear winner of the bold, crisp, and delicious exchange between Warren and Buttigieg, though, was not the senator from Massachusetts or the mayor from South Bend: It was the senator from Vermont, Bernie Sanders.

Sanders’ team of surrogates had come prepared for a showdown about the wine cave: Senior aide Jeff Weaver and national co-chairwoman Nina Turner both wore black T-shirts emblazoned with the URL to a website called PetesWineCave.com. (The link redirected to a fundraising page for Sanders.) “You see my T-shirt?” Turner asked reporters. “Yeah, we want to have this fight.”

But it was Warren who brought up the cave, and Warren who drew the counterattack from Buttigieg. In the post-debate spin room, Sanders’ supporters seemed practically giddy that two of their candidate’s biggest rivals had spent the most memorable moment of the debate tearing each other down on what has long been one of his signature issues, the corrupting influence of money in politics.

The fight was particularly good for Sanders for a couple of reasons. First, he barely muddied himself in it, taking what felt like one minor and relatively friendly shot at Buttigieg and Biden for their fundraising among billionaires. Warren and Buttigieg, meanwhile, took center stage in a dogfight that likely did not play well for either side. “When Democratic candidates attack each other over who is friendlier to billionaires, their voters hate it,” reported Republican pollster Frank Luntz, who conducted a debate focus group for the Los Angeles Times. “Dem voters want to hear them attack problems, not each other.” The Warren-Buttigieg sniping allowed Sanders to appear to remain above the fray.

The second reason why this was a clear win for Sanders is that money in politics is an issue on which, as his surrogates were eager to point out, both Buttigieg and Warren are more vulnerable than him.

“Every single candidate [on that stage] has taken some money from billionaires except for Bernard Sanders,” Turner said to reporters, in a clear reference to Warren.

Weaver was more explicit, noting that Warren had paid for a Democratic National Committee voter database with money from a California multimillionaire.

“Her campaign enticed a big donor in California to give $100,000 to the Democratic Party to pay for her voter file,” Weaver said. “That’s $100,000 essential benefit from one big donor. We don’t do that. We pay for our voter file with the DNC with our $18 contributions.”

Similarly, Buttigieg, besides defending rich people’s right to participate in politics, had hit Warren for hypocrisy and what he called a “purity test” standard she may not be able to pass. After the debate, Warren was peppered with questions from TV reporters about having accepted large-donor contributions to her Senate campaign fund, $10.4 million of which she transferred to her presidential campaign.

“For six years you did raise money,” David Axelrod pointed out on CNN. “Did you feel corrupted by the money you were raising?”

Her answer was oblique. “I saw what it is that people expect in return,” Warren said of her change of heart. “I understand that the American people who watch this government work better and better and better for giant corporations and rich people want to hear someone who credibly can say I can take on the billionaires.”

When asked a similar question by a PBS reporter, Warren’s answer focused on the relative amounts of money involved.* “I raised more than twice the amount of money that I put into my presidential campaign through small-dollar donations,” Warren said. “But this is about what we’re doing right now this year. What kind of conflicts are we are creating?”

This sort of muddled history, though, speaks to another of Warren’s vulnerabilities that Sanders’ surrogates seemed eager to exploit: that she has been wishy-washy in her support for the aggressive left-wing proposals Sanders has consistently championed.

“He has stood constantly and strong for ‘Medicare for All.’ He doesn’t change his positions when things are not polling well,” Turner said in another apparent dig at Warren, who has backed off her full-throated support for single-payer health care in recent weeks. “He doesn’t change his position when the heat comes.”

Maybe it was a little ungracious of the Sanders camp to be harping on the ideological differences between their candidate and Warren, on a night she delivered their prepared criticism of Buttigieg for them, without the Vermont senator having to lift a finger. “Now he’ll be known as the wine cave candidate, I guess for the rest of his life,” CNN’s Gloria Borger commented of Buttigieg after the debate.

Indeed, questions about wine caves dominated the post-debate conversation in the spin room. When I walked by California Gov. Gavin Newsom, he was being asked about wine caves and sticking up for one of his state’s major agricultural products.

“In California, we’re very proud of our wine industry,” Newsom said. “It’s one of America’s great exports. It’s also a wonderful job creator. So, we should be a little sensitive about that.”

The focus on wine caves allowed Sanders’ surrogates to paint Buttigieg—who has taken the lead in the Iowa caucus as Warren and former Vice President Joe Biden have fallen and Sanders has climbed into second place according to the most recent polling average—as an out-of-touch elitist who will be as vulnerable to Donald Trump as Hillary Clinton was.

“It’s like new packaging, same old product,” Weaver said. “It failed [against] Trump. Why would we want to do it again?”

Backstage, Buttigieg’s surrogates again cited the hypocrisy defense, to which Warren is much more vulnerable than Sanders.

“Pete’s demonstrated so much strength as a leader and so much integrity that […] the best folks could bring this time was a complaint about a fundraisers that each and every one of them have had in their careers in the Senate or elsewhere in government,” West Sacramento Mayor Christopher Cabaldon told me.

Buttigieg’s team was also eager to paint the attacks on their candidate as the perils of running a leading campaign.

But when I asked West Hollywood Mayor Pro Tempore Lindsey P. Horvath how many questions the group had received that night about wine caves, she didn’t want to answer directly. “Not as many questions as we’ve gotten about people coming for Pete, but that’s what you expect when you’re in the front-runner position,” Horvath said.

It seems unlikely that Thursday’s debate made his position more favorable. The most recent poll from Iowa State University has Sanders currently sandwiched between Buttigieg and Warren in Iowa with 21 percent to Warren’s 18 and Buttigieg’s 24.

According to Luntz’s Los Angeles focus group, nine people thought Warren won the debate. Fourteen people thought Sanders, who only had six supporters at the start of the night, won. Zero people in that survey thought Buttigieg won.

Correction, Dec. 20, 2019: This article originally misidentified a PBS reporter as a CBS reporter. Update, Dec. 20, 2019, at 3:09 p.m.: This article has been updated to reflect that Frank Luntz corrected the number of people who thought Sanders won the debate.