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Senator Bernie Sanders of Vermont raised $44 million in March, his campaign announced Friday, beating his previous best monthly haul.

The strong fund-raising numbers followed a string of victories in Democratic voting contests last week in Idaho, Washington, Alaska, and Hawaii. They also hint at the seemingly limitless well of small dollars that Mr. Sanders has been able to tap, even as his chances of winning enough delegates to take the Democratic nomination appear to be waning. Should the Democratic front-runner, Hillary Clinton, post a lower number, it would be the third consecutive month that Mr. Sanders raised more money than the former secretary of state.

“Working people standing together are going to propel this campaign to the Democratic nomination and then the White House,” Mr. Sanders said in a statement.

Mr. Sanders has depended almost exclusively on millions of grass-roots supporters making repeated small contributions. Such supporters can give again and again without hitting federal contribution limits. According to his campaign, more than two million supporters have made more than six million contributions.

His success in tapping those donors — and at repeatedly out-raising Mrs. Clinton, one of the best-connected politicians in the country — hints at how Mr. Sanders has reordered the role of money national campaigns. And the surge of money comes as Mr. Sanders prepares to compete against Mrs. Clinton in New York, the most expensive media market in the country.