Bernie Sanders raised $25.8 million in April -- short of his campaign's hauls of $44 million in March and $43.5 million in February.
The latest numbers could keep the Vermont senator ahead of Hillary Clinton -- who has not yet released her April figures -- in the Democratic fundraising race.
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But the dip from the previous month comes as the contest approaches its last states to vote, with Sanders increasingly trailing Clinton in votes, pledged delegates and overall delegates, and suffering defeats in five out of six recent East Coast primaries, including New York.
His campaign hasn't said how much cash Sanders currently has remaining in his campaign's bank.
A defiant Sanders has insisted he'll continue through California's June 7 primary in a bid to win -- or at least carry as much influence as possible into the Democratic National Convention in Philadelphia.
His campaign said after April, it has received 7.4 million total contributions from 2.4 million individual donors, totaling $210 million.
It pointed out that his nearly $26 million April haul topped Clinton's $21 million in March. Clinton has not yet released her April numbers.
"What our campaign is doing is bringing millions of Americans into the political process," said Jeff Weaver, Sanders' campaign manager, in a statement accompanying a news release announcing the April numbers.
"Sanders is the candidate with the most energy and excitement," Weaver said. "He is the candidate with the best chance of winning in November. He is the candidate who is in the best position to bring a new generation of voters into the democratic process and restore the faith of working-class voters that we can have a government that works for all of us, not just the 1 percent."
There are 14 Democratic contests left in states and territories. Next up is Indiana on Tuesday. Last is the District of Columbia on June 14.