And for the second consecutive quarter, Mr. Biden, a two-term vice president who previously served in the Senate for 36 years, was bested by Mr. Buttigieg, the mayor of the fourth most populous city in the 17th most populous state .

Ms. Warren’s campaign said on Friday that it had received 943,000 donations in the third quarter from 509,000 donors, and more than 300,000 of those donors gave to her presidential campaign for the first time. The average donation was $26, and Ms. Warren ended the quarter with $25.7 million in cash on hand, according to her campaign.

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“Please take a moment to be proud of the movement you’re helping build ,” Roger Lau, Ms. Warren’s campaign manager, wrote in an email to supporters. “Close your eyes and picture Wall Street bankers scowling into their catered breakfast,” he suggested.

Collecting small contributions from a vast group of donors comes with a huge long-term advantage: Those donors can keep giving again and again as the campaign goes on. That is not the case for wealthy donors writing $2,800 checks to candidates — the maximum an individual can give to a campaign for the primary race.

Ms. Warren and Mr. Sanders “are breaking these old political models in which rich donors can capture and control political parties,” said Stephanie Taylor, a co-founder of the Progressive Change Campaign Committee, which is supporting Ms. Warren. “This is just a really revolutionary, seismic shift in American politics.”

Beating Mr. Sanders’s total for the past three months would have given another jolt of momentum to Ms. Warren’s campaign. Instead, Mr. Sanders’s status as the top fund-raiser for the quarter provides a reminder of his sizable base of support, even as other indicators like polling are less favorable.

In the long run, Mr. Sanders’s slight financial edge over Ms. Warren in the quarter is unlikely to make a major difference in the perceptions of their candidacies. Mr. Sanders entered the race having already established an enormous network of donors during his 2016 presidential campaign, and he raised slightly less in the third quarter of 2019 than he did during the same time period in 2015.