During this week’s Democratic Party’s debate in Los Angeles, Mr Buttigieg clashed with progressive senator Elizabeth Warren, over the event he held at the Hall Rutherford Winery in Napa Valley.
“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.”
Mr Buttileg was quick to fire back, pointing to a Forbes magazine article that said he was the only individual among the seven on stage who was not a “millionaire or a billionaire”.
“So, this is important. This is the problem with issuing purity tests you cannot yourself pass,” he said.
On Saturday, attending a rally with fellow progressive Bernie Sanders, Ms Ocasio-Cortez attacked the mayor of South Bend without naming him.
“This is the revolution,” she said, speaking at Venice Beach. “And by the way, anyone who accuses us of instituting purity tests, it’s called having values, it’s called giving a damn.”
Ms Ocasio-Cortez, who once worked as a waitress, added: “Let me tell you something I go to work all the time and I hear people say, “what will my donors think”? I hear that phrase. And I hear and I see that billionaires get members of Congress on speed dial and waitresses don’t.”
Mr Sanders, who has been endorsed for the presidency by Ms Ocasio-Cortez, the youngest ever member of Congress, also referred to Mr Buttigieg’s fundraising.
“We don’t go to rich people’s wine caves,” he said, according to the Daily Mail.
Meanwhile, the owners of the winery where the event was held, Craig and Kathryn Hall, took issue with how their wine cave has been portrayed in the media.
“It seems someone’s intentionally trying to create a different image than the reality. And that’s unfortunate,” Mr Hall told the Associated Press.
“I don’t think anyone came with the expectation that they were going to become Pete’s good buddy for some personal purpose.”
A spokesperson for the mayor’s campaign said of the congresswoman’s comments: “The stakes are too high for purity tests on fundraising or ideology that turn away resources and risk alienating voters. We need to do everything we can to defeat Donald Trump and elect Democrats up and down the ballot.”
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