Democratic presidential hopefuls Sen. Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE (Mass.) and South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBillionaire who donated to Trump in 2016 donates to Biden The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice MORE went head-to-head on Thursday over wealth and high-dollar fundraising in the sharpest clash of the debate thus far.

In an escalation of their simmering feud, Warren took aim at Buttigieg for holding a fundraiser in a wine cave in Napa, pointing out that although Buttigieg pledged to have open fundraisers, this one was closed. In fact, the fundraiser in question was open to the press.

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

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Buttigieg defended his campaign's fundraisers, saying his campaign needs support from everybody looking to defeat President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE in 2020.

"You know, according to Forbes Magazine, I am literally the only person on this stage who is not a millionaire or a billionaire," Buttigieg responded. "This is the problem with issuing purity tests you cannot yourself pass. If I pledged to never be in the company of a progressive, Democratic donor, I couldn't be up here."

"Billionaires in wine caves should not pick the next president of the United States."



Sen. Warren at the #DemDebate criticizes a recent Pete Buttigieg fund-raiser that included $900 bottles of wine (via @QuickTake)



Follow along LIVE https://t.co/beg3ZUl6jY pic.twitter.com/Kg3jmvZvBJ — Bloomberg Politics (@bpolitics) December 20, 2019

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Klobuchar to Buttigieg and Warren: "I did not come here to listen to this argument" #DemDebate https://t.co/SEXTYFvSuu pic.twitter.com/0faQjSGwQJ — CNN Politics (@CNNPolitics) December 20, 2019

"Senator, your net worth is 100 times mine," Buttigieg continued, adding that it would not be wrong if someone donated the maximum legal amount of money to his campaign.

"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 from everybody who is committed to defeating Donald Trump," he said.

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Sen. Amy Klobuchar Amy Klobuchar3 reasons why Biden is misreading the politics of court packing Social media platforms put muscle into National Voter Registration Day Battle lines drawn on precedent in Supreme Court fight MORE (D-Minn.) jumped into the fray, saying she did not come to the debate to listen to Warren and Buttigieg spar.

"I've never even been to a wine cave. I've been to the wind cave in South Dakota, which I suggest you visit," she said.

--Updated at 1:17 a.m. EST.