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Senator Bernie Sanders’s presidential campaign raised more than $33 million in the final three months of 2015, as his wide base of small-amount donors enabled him to come within $4 million of the amount raised by Hillary Clinton, his rival for the Democratic nomination, his campaign said Saturday.

Mr. Sanders, a senator from Vermont, has now raised $73 million for his nomination fight, his aides said in a news release.

The campaign said more than one million individual donors had made more than 2.5 million contributions, passing President Obama’s previous record of about 2.2 million for the number of individual donations, which was set at the end of 2011.

“This people-powered campaign is revolutionizing American politics,” Jeff Weaver, Mr. Sanders’s campaign manager, said in a news release accompanying the release of the figures.

Mr. Sanders’s spending on the campaign also appears to have shot up. The campaign now has $28.4 million in cash left from the $73 million raised, the release said.

The release announcing the haul was replete with references to how, “unlike other campaigns,” Mr. Sanders was doing well with small-amount donors. The references were a veiled shot at Mrs. Clinton, who raised $37 million in the last quarter and has taken in more than $112 million in donations over all. Mrs. Clinton also has a “super PAC” supporting her.

Mr. Sanders’s campaign has aggressively targeted and courted low-dollar donors, developing a deep network of people it could keep tapping for new contributions.

Mrs. Clinton, by contrast, struggled in the second and third quarters of the year to establish a low-dollar donor base, relying primarily on fund-raising events with ticket prices of $2,700 to bring in donations..

Last month, Mr. Sanders’s team said in a court filing related to a lawsuit against the Democratic National Committee over a denial of access to voter data that it anticipated losing $600,000 a day in donations. A spokesman for the campaign, Michael Briggs, said that was a reference to a short window of time and did not reflect the campaign’s daily intake of contributions.

Two of the Republican candidates, Senator Ted Cruz of Texas and Ben Carson, have released their fund-raising totals for the quarter. Mr. Cruz raised $20 million, a two-thirds increase from his previous quarter, and Mr. Carson raised $23 million.