The DNC’s September fundraising marks the best month of the 2010 cycle for the DNC and the best month of cash collection for the committee in a midterm election since the passage of the McCain-Feingold campaign finance law early last decade.

Official numbers for September aren’t due at the Federal Election Commission until Oct. 20. The Republican National Committee, which has struggled on the fundraising front in recent months, has not yet released its September figures.

Of the $16 million the DNC raised in September, more than 80 percent came from online and direct-mail donors — evidence that the party base is starting to vote with their checkbooks, argued DNC officials.