Democratic presidential candidate Bernie Sanders (I-Vt) has raised more than $15 million for his presidential campaign, according to a Federal Election Commission document that reveals the vast majority of those contributions totaled $200 or less.

The Sanders campaign reported to the FEC Wednesday that it raised nearly $10.5 million in small contributions, and an additional $3 million in donations of more than $200 each. That $13.5 million fundraising haul -- which accounts for money he has raised since he announced his candidacy in late May -- was bolstered by an additional $1.5 million he transferred from his Senate campaign account.

The campaign is likely to use the larger-than-expected fundraising tallies, particularly his impressive haul among the grassroots, to reinforce the senator's claim to speak for Democratic Party base.

In addition to his strong support among small donors, the second quarter FEC filing reveals the campaign has spent around $3 million. The bulk of those expenditures have gone to digital consulting and media advertising, on which the campaign spent about $1.3 million. Besides spending $350,000 on printing and mailing services, the campaign's remaining costs have been primarily operational.