Vermont Sen. Bernie Sanders, running in the Democratic presidential primaries, has raised about $15 million, his campaign said Thursday.

His campaign emphasized the grass-roots strength of his fundraising: 250,000 donors making nearly 400,000 contributions of $250 or less.

The numbers come from a quarterly disclosure report being filed at the Federal Election Commission, and are measured from when Sanders launched his campaign April 30.

The maximum legal contribution to a presidential candidate is $2,700. The Sanders campaign said its average contribution was $33.51.

The campaign said supporters gave "almost entirely with online donations."

Reliance on small donors cuts both ways. They provide a candidate with a ready-made network and grass-roots credibility — but it would take 80 donors giving that average $33.51 contribution to match one wealthier donor writing a check for $2,700.

The fundraising announcement came the morning after Sanders drew 10,000 supporters to a rally in Madison, Wis. — a signal that Sanders has drawing power among the liberal faithful.

Sanders' quarterly total is about equal to that of Priorities USA Action, the leading super PAC in the Clinton network. Clinton, who launched her campaign on April 12, just a couple of weeks before Bernie Sanders, reportedly raked in $45 million in her first quarter.

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