Sen. Barack Obama raised $66 million in August, making it his best month ever and the best in American political history, an aide said Sunday morning.

    Obama is releasing that number after suggestions that his fundraising was failing to meet expectations. It puts him on pace to substantially outspend John McCain in the last two months of the race, in which McCain will be limited to spending the $84 million supplied by the Treasury under public financing rules.

    Obama's large take, and the expectation that he'll raise even more in the race's final two months, may put to rest some Democrats' worries that he'd made a mistake by opting out of public financing.

    It doesn't mean the Democrats will outspend the Republicans this year, though. The Republican National Committee's cash advantage over the Democratic National Committee, in combination with swelling outside spending, will likely allow McCain to level the playing field, though the fact that Obama has raised the money himself, in small chunks, gives him direct control over how it's spent, and fewer concerns about technical limits on spending.

    An Obama aide said the campaign added 500,000 new donors to its rolls in August. The new figure - which shatters his previous one-month record of $55 million - also demonstrates how the increasingly heated, nasty race has energized Obama's fundraising and raises expectations that he will raise that much or more in each of the next two months.

    Obama's tally suggests that McCain's late-August choice of Sarah Palin, which has energized conservatives - though largely too late for them to contribute directly to McCain's campaign - may also wind up deepening Obama's reserves when its full effect is felt in his September report.

    The McCain campaign raised $47 million in August.

    Obama spokesman Bill Burton said that the Obama campaign had $77 million on hand; it had just under $66 million on hand at the end of July, meaning that it spent roughly $55 million last month.