WASHINGTON — Republican Mitt Romney thumped President Barack Obama in campaign fundraising in May, and while the incumbent's team is dismissing the surge, it could sow concern among Democrats five months from the election.

Figures released Thursday show Romney outraised Obama for the first time in the White House race, with the challenger raking in more than $76 million, nearly 30 percent more than the president's campaign haul.

But Obama's campaign warned that the unseen money flooding the presidential race, through outside groups unrestricted by campaign finance rules, would be the financial gamechanger in 2012.

Obama, who proved himself a fundraising juggernaut during his presidential run four years ago, raised "more than $60 million" in May along with the Democratic National Committee and local committees, his campaign said.

That's a monthly record for the president's re-election bid, but the fact that Romney shot past him suggests the dash for campaign cash over the coming months will be fiercely competitive ahead of November's polls.

It also shows Romney is unmistakably on a roll since becoming the all-but-certain nominee more than one month ago, following a bruising primary battle against Republican rivals.

An emboldened Romney lambasted Obama on the campaign trail Thursday over the the president's "misguided policies," which he said have led to chronically high unemployment and lack of leadership and direction.

"When you look around at America's economy, three and half years into this presidency, it's painfully obvious that this inexperienced president was simply not up to the task of solving a great economic crisis," Romney told supporters in St. Louis, Missouri.

"As your president, starting on Day One, I will do everything in my power to end these days of drift and disappointment."

Romney's camp said he and the Republican National Committee raised $76.8 million in May, and they have $107 million in cash on hand.

The impressive haul was not unexpected, as May was the first full month in which the RNC was able to fundraise in conjunction with Romney.

That was the storyline the Obama campaign was pushing after the figures came out.

"We knew that this day would come," Obama campaign spokesman Ben LaBolt told reporters.

"The RNC and the Romney campaign just established their joint committee which means all the primary donors who had written the maximum contribution during the primary can now go back and make the same contribution for the general election."

But the Republican camp was quick to suggest Democrats might be turning on Obama and donating to Romney.

"Whether (Romney donors) are Republican, Democrat, Independent, a first time political donor or a former Obama donor, this is not just a campaign; it's an opportunity for the country," Romney's finance chairman Spencer Zwick said.

"It is clear that people aren't willing to buy into 'hope & change' again," he added, referring to an Obama slogan from 2008.

Polls show a tight race, with many putting the rivals neck and neck.

Romney's campaign said 93 percent of the May donations -- more than 297,000 of them -- were $250 or less. Those donations raised $12 million out of the total.

Obama pulled in far more individual donors, however, at 572,000, with 98 percent of them giving less than $250.

The numbers do not, however, take into account contributions from outside groups called "super-PACs," which can raise and spend unlimited money to support candidates but cannot directly fund a campaign.

The Obama campaign strongly suggested they were more concerned about superPACs than Romney campaign money.

"We'll be the first president to be outspent not because of what Romney's raising," said Obama campaign strategist David Axelrod.

"You have things like the Koch brothers saying they'll spend $400 million," he said.

The billionaire founders of Koch Industries are deeply involved in funding conservative advocacy groups, and they'll leverage such extraordinary amounts of funding "through their secret organizations, the ones that don't disclose," Axelrod said.

"It should be a source of concern to everyone."

Fundraising is vital to US presidential elections, when candidates criss-cross the country for months and roll out several advertising campaigns, spending hundreds of millions of dollars in the process.