The impressive haul tops the $18 million raised last quarter by Bernie Sanders, who led the Democratic field in fundraising during that period. It will help Buttigieg transition from a scrappy startup operation to a more formidable campaign for the 2020 Democratic nomination and give him staying power to weather the summer months, when fundraising typically dries up.
Meanwhile, many of his better-known rivals have struggled to raise money and could face more challenging circumstances. "He did exactly what you are supposed to do," said Rufus Gifford, who was finance director of President Barack Obama's 2012 campaign. "They are seizing on opportunities, they are building infrastructure, hiring staff and working their butts off."
Campaigns often release an early glimpse of their end-of-quarter fundraising, particularly if the numbers are good. So far, none of his rivals have followed suit, though they have until July 15 to report the numbers to the Federal Election Commission.
The figures will be a crucial factor in determining which candidates qualify for the September debate stage. Buttigieg, 37, surprised many people with a first quarter haul of roughly $7 million, which topped many of the better-known candidates in the race. Since then, he's parlayed his biography as a gay military veteran and Rhodes scholar who was twice elected to lead the Rust Belt city of South Bend into becoming one of the hottest tickets in Democratic fundraising.
"The LGBT community is very enthusiastic about supporting him," said Gifford, who is gay. "That does not mean they are going to vote for him. But they want to support the candidacy because it's historically important."
Buttigieg's campaign says he has $22.6 million cash on hand and received money from donors from all 50 states, as well as U.S. territories, with an average contribution of about $47. His campaign says that will allow him to build out an operation in early voting states, including Iowa, New Hampshire, South Carolina and Nevada. Already, his staff has grown from a handful of strategists and volunteers to a headcount that exceeds 100. Recently, his South Bend headquarters moved into a larger office.
While Buttigieg has drawn swooning donors, he still faces significant challenges. For one, his support with African Americans in public opinion polls is dismal, raising questions about his ability to build a winning coalition in an increasingly diverse Democratic Party.
As most candidates were furiously trying to raise money during the last two weeks before the June 30 deadline, Buttigieg had to cancel a California fundraising trip to deal with unrest at home after a white South Bend police officer shot and killed a black man who police say was armed with a knife.
"Clearly his support is not coming from people of color, yet he is getting lots and lots of donations," said Steve Phillips, an African American civil rights attorney whose Dream United super PAC is supporting New Jersey Sen. Cory Booker, who is black. "In order to win, there has to be an enthusiastic and large turnout of voters of color."
For now, Buttigieg is doing well enough in overall polls and has received contributions from more than 400,000 people, securing his spot in the September debates. The Democratic National Committee requires participants to hit 2% in multiple polls and 130,000 individual donors. Although many campaigns are worried, DNC Chairman Tom Perez has resisted pressure to relax the requirements.
Currently, the only other locks for the fall debates are former Vice President Joe Biden, Sanders, Massachusetts Sen. Elizabeth Warren and California Sen. Kamala Harris. Although his rivals have yet to release their numbers, Biden hinted last month that he's taken in a similar amount to Buttigieg.
Biden has said his campaign had amassed 360,000 donors, who gave an average of $55 apiece. The math suggests he collected about $19.8 million since entering the race in April, but his campaign declined to confirm the figure at the time.
His campaign remained coy on how much he has raised but told supporters in an email on Monday that they "blew our fundraising goal out of the water."
Associated Press writer Sara Burnett contributed to this report from Chicago.