SOUTH BEND, INDIANA - APRIL 14: South Bend Mayor Pete Buttigieg announces that he will be seeking the Democratic nomination for president during a rally in the old Studebaker car factory on April 14, 2019 in South Bend, Indiana.

Particularly, Buttigieg's sincere approach is generating enthusiasm among the Democratic donor class. One of the leading names on the list, lobbyist and former John Kerry 2004 campaign official Steve Elmendorf, decided to back Buttigieg on Sunday, the day the mayor officially launched his campaign with a speech in South Bend.

The financiers on the roster range from former U.S. ambassadors to real estate executives, the latest evidence that the South Bend, Indiana, mayor's underdog bid to challenge President Donald Trump next year is catching on with Democrats as the party sorts through a crowded primary field.

Pete Buttigieg's increasingly popular presidential run has drawn the support of more than two dozen top Democratic fundraisers, including people who bundled big-dollar donations for Barack Obama and Hillary Clinton during their White House bids, according to a list CNBC obtained from campaign aides.

"The more I watched him, the more I thought he was performing at a level above all the other candidates. He has an optimistic message and I liked him," said Elmendorf, who bundled more than $100,000 for Clinton's 2016 campaign, according to the nonpartisan Center for Responsive Politics. "I just think everything about him is the opposite of Trump in a good way and when he answers every question he's trying to find solutions. He's not attacking anyone."

"I think he's put himself out there in every possible venue. He's done every possible interview and has done well. He comes across as authentic," he said. "There's something to be said about someone from out of Washington and a new, young person in this race."

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Film producer and environmental activist Laurie David is another prominent member of the Buttigieg bundling list. The ex-wife of "Curb Your Enthusiasm" creator Larry David, Laurie David produced the Oscar-winning climate change documentary "An Inconvenient Truth."

Members of the wealthy Pohlad family – which owns a group of more than 30 Minneapolis-based businesses, including Major League Baseball's Minnesota Twins – are also backing Buttigieg. According to Forbes, the family's total net-worth as of 2015 was $3.8 billion. Robert Pohlad backed Obama in 2012 and helped rake in at least $500,000 that cycle.

Jill Goldman, a Los Angeles activist and filmmaker who was a member of Obama's 2008 national finance committee, is also behind Buttigieg. She helped Obama bring in at least $200,000 throughout his first run for the White House.

John Phillips, who previously was U.S. ambassador to Italy under Obama, is also on the list. He is a founding partner at legal powerhouse Phillips & Cohen, and he raised at least $500,000 for Obama in 2012.

David, Goldman and Phillips did not return requests for comment. Pohlad could not be reached. CNBC also reached out to others on the list.

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Hedge fund executive and bundler Orin Kramer is also backing Buttigieg. The New York Times and CNBC earlier reported Kramer's support for the South Bend mayor.