Mitt Romney’s campaign fundraising significantly outpaced President Obama’s effort for the first time last month, increasing the likelihood that the Republican presidential candidate and his allies will far outspend their Democratic opponents by November.

Romney and the Republican National Committee said Thursday that they raised a combined $76.8 million in May, which is nearly as much as the presumed nominee brought in during the GOP primary season. Obama and the Democratic National Committee amassed $60 million in what was their best month so far, campaign officials said.

Romney’s monthly haul serves to undercut Obama’s reputation as the nation’s preeminent political fundraiser and signals a growing confidence among Republicans that the former Massachusetts governor has a strong chance of defeating the incumbent. The money woes add to the worries facing Obama, who is struggling with a wheezing economy and precarious approval ratings.

The fundraising arms race has become one of the central features of the 2012 campaign, as each candidate crisscrosses the country for donor events on an almost daily basis. The presidential contest alone could spur well more than $2 billion in spending by campaigns, parties and interest groups, with a likely advantage for Republicans.

“This is clearly an alarm,” said Clinton administration veteran Paul Begala, who advises a pro-Obama super PAC that has struggled to raise money from liberal donors. “I sure hope my Dems don’t hit the snooze button. I have been saying for some time that this thing is far from in the bag. It’s not even in the shopping cart.”

Brian Ballard, who chairs Romney’s fundraising operation in Florida, said that “there’s just this awakening that we have to turn the country around and that Mitt actually could win. There’s an expectation and belief in victory.”

Obama campaign aides said they had expected Romney to post strong fundraising numbers after clinching the Republican nomination in mid-April, and they maintain that the major financial threat to the president will come from super PACs and other conservative groups that can raise unlimited amounts of money.

Jim Messina, Obama’s campaign manager, sent a fundraising e-mail to supporters Thursday afternoon with the subject line “We got beat.”

Obama spokesman Ben LaBolt told reporters that “we knew this day would come,” noting that John F. Kerry outraised President George W. Bush by 2 to 1 after becoming the Democratic nominee in 2004.

“We anticipated that they would beat us this month,” LaBolt said. “We’re focusing on continuing to grow our donor base.”

Even with his strong May fundraising, Romney could still have difficulty catching up to Obama, who has been stockpiling cash for more than a year and building campaign offices nationwide.

The Romney team and the RNC said they had $107 million in cash on hand at the end of May. The Democrats, who did not release a May cash estimate, had nearly $140 million on hand at the end of April between Obama and the DNC. Official disclosure reports are not due until June 20.

Romney raised more than Obama in May, the first full month of joint fundraising between the presumptive GOP nominee and the RNC. (The Washington Post/Source: The campaigns)

Romney also continues to lag behind Obama in the proportion of donors who give small amounts, and many of Romney’s supporters will be unable to give any more under federal campaign limits. About 15 percent of Romney’s May total was donations of $200 or less; Obama has raised about 40 percent of his money from the smallest donations.

Asked by reporters about his fundraising haul following a speech in Missouri on Thursday afternoon, Romney said only: “Long way to go.”

Since securing the GOP nomination, Romney has devoted himself to raising money. Nearly every day, his schedule has been a whirl of hotel ballrooms and private mansions, of chicken skewers and cheap wine in plastic cups.

Obama’s pace has been less frenetic, though not much: He held his 150th fundraiser of the 2012 cycle with a gay-focused event in Los Angeles on Wednesday, followed by an event with African American donors on Thursday.

“I am confident that everyone in that room will do whatever they can to make sure he has the resources needed to win in November,” said California lawyer Dana Perlman, a top Obama bundler.

But Romney fundraisers have become equally confident, and they say Romney’s success in vanquishing Rick Santorum, Newt Gingrich and other GOP opponents has breathed new life into a fundraising effort that often struggled during the primaries.

“Do we have a good fundraising organization? Yes. Do we have a fine candidate who will make a fine president? Absolutely,” said Fred Malek, who has been raising money for Republicans since the Richard M. Nixon era. “But beyond that, there is great alarm about the present direction of the country that puts all of the above in bold type and underlined. That’s what’s happening.”

Casino moguls Sheldon Adelson and Steve Wynn have mobilized their networks in recent weeks on Romney’s behalf, while a few prominent supporters of Obama’s in 2008 — including New York publisher Mort Zuckerman and Chicago businesswoman Susan Crown — have gone all out to raise money for Romney since the primaries ended.

Romney’s fundraisers acknowledge that Romney has reached for relatively low-hanging fruit during his May-to-June fundraising sprint and must now push to keep up the pace. Romney’s top 100 bundlers — “Team 100” — are heading to a private retreat in Utah on June 22-24 to plot out how to replicate the May success in the months ahead. Unlike Obama, Romney has not publicly identified most of his top campaign bundlers.

“We thought we were going to outraise Obama, but to outraise him by $17 million is really quite something,” said Bobbie Kilberg, a key Romney fundraiser in Virginia. “You really can feel something happening here, and I think absolutely we will catch up with him overall.”

Rucker reported from Missouri. Staff writers Aaron Blake in Washington and Amy Gardner in Los Angeles contributed to this report.