Charles Rex Arbogast, Associated Press
Mosaic of Obama's face made of newsprint from a local newspaper dominates a wall of his headquarters in Chicago.

CHICAGO (MCT) — Potentially offering some relief for increasingly nervous Democrats, Sen. Barack Obama's campaign said Sunday that he raised $66 million in August, his top month ever and easily a monthly record for presidential fundraising.

Adding more than 500,000 new donors during the month, his campaign said it has now received contributions from more than 2.5 million people since the start of Obama's 19-month-old presidential bid.

With advertising and get-out-the-vote spending already ratcheting up in advance of the Nov. 4 election, Obama's aides said the campaign ended August with $77 million in the bank.

The Illinois Democrat's previous best month was February 2008, when he raised $55 million amid an intense nomination fight with Sen. Hillary Clinton.

Still, Obama will have to match or exceed his August pace if he is to meet his campaign's goal of raising $300 million during a five-month period that ends in October. Combined with primary campaign fundraising, Obama appears poised to raise more than a half-billion dollars before November.

Sen. John McCain, the Republican nominee, raised $47 million in August, more than double his previous best fundraising month. The Arizona Republican's month was boosted in large part by what his campaign has said was a burst of $10 million in contributions shortly after he named Alaska Gov. Sarah Palin as his running mate.

Unlike Obama, McCain is getting $84 million in public money for his fall campaign because he agreed to accept fundraising and spending limits, as have all previous presidential nominees since the public financing system was established more than three decades ago following the Watergate scandal. Obama decided to bypass the system, allowing him to raise and spend as much as he likes.

McCain will also benefit from more successful collections by the Republican National Committee, as compared to the Democratic National Committee.

Obama spent a rare day off the campaign trail — working out, getting a haircut, hanging out at home in Chicago and visiting his campaign headquarters downtown — before stopping by the office of his chief strategist, David Axelrod.