The national campaigns backing President Obama and Republican challenger Mitt Romney are drawing even in their fundraising prowess, but new financial filings released show that the "super" political committees supporting the GOP candidate and his party are widening the money gap over struggling pro-Democratic party organizations.

The main pro-Romney super PAC, Restore Our Future, on Wednesday reported raising $8 million in May, giving it a total of $64 million so far. The group spent more than $55 million to defeat Romney's opponents during the GOP primary, and it is now reaping high-dollar financial aid from both veteran Romney supporters and from donors who once backed his rivals.

A political committee backing Obama, Priorities USA Action, posted its strongest one-month total by raking in $4 million in May, a sign that Democrats had begun digging deep into their wallets after months of hesitance. But the pro-Obama group was still left in the dust -- not only by the Restore committee's strong performance but also by the latest tally from American Crossroads, a Republican super PAC formed by GOP strategist Karl Rove. It raised $4.6 million in May.

After early months that saw Obama reach impressive fundraising totals echoing his campaign's record-breaking $750 million haul in 2008, the changing calculus raises the prospect that he could become the first incumbent president outspent by his challenger. Romney's national campaign joined with the Republican Party in May to raise more than $76 million, outpacing Obama and the Democrats' $60 million haul during the same period.

Super PACs can raise and spend unlimited amounts of cash but are not allowed to coordinate their efforts with the candidates they support. The national presidential campaigns can devote their cash both to media and Web ads and to turn out party faithful, but the super PACs tend to spend most of their war chests on media campaigns.

The latest financial filings for the pro-Romney Restore committee show that while he was consolidating his position as the GOP favorite, backers of some of his opponents were shifting their financial allegiance to his cause -- even as some of his loyal super PAC backers dug deeper to bankroll the committee's tough media ads now targeting Obama.

The biggest contributions to Restore Our Future in May came from a trio of firms linked to a Houston-based businessman who previously supported a Romney rival, Texas Gov. Rick Perry. The disclosures show that three companies based at the same post office box office in Dayton, Ohio, each gave $333,333 to the pro-Romney super PAC. Corporation records show the firms are headed by Houston businessman Robert T. Brockman, who missed giving the super PAC a rounded-off $1 million donation by a single dollar.

Brockman heads the Reynolds and Reynolds Co., an Ohio-based firm that provides computer and software systems for auto dealerships. Brockman's personal website lists him only as chairman and CEO of the Reynolds and Reynolds Co., but his name is not listed with any of the Dayton donations. Calls to Brockman at his office in Houston were not immediately returned to The Associated Press.

Although super PACs are required to divulge all their donations, loose disclosure rules allow contributors to withhold their names and mask their donations by setting up limited liability corporations or other front companies. One of Restore's first donors, Edward Conard, made a $1 million contribution last year behind a front company, W Spann LLC, until public pressure forced him to acknowledge his name and affiliation with Romney's former private equity firm, Bain Capital.

Brockman's firm, Reynolds and Reynolds, was one of more than 60 companies that wrote to three Obama administration Cabinet officials last October, urging them not to overburden employers with "unnecessary expenses" as part of the new health care law. In the Oct. 21, 2011, letter to Treasury Secretary Timothy Geithner, Health and Human Services Secretary Kathleen Sibelius and Labor Secretary Hilda Solis, Reynolds and Reynolds and the other firms -- they included the U.S. Chamber of Commerce -- also urged an extension of a deadline for them to provide health benefit summaries to U.S. agencies.

Before his companies donated to the pro-Romney group, another firm linked to Brockman had previously given $50,000 to Perry. The $50,000 donation to the pro-Perry Restoring Prosperity Fund came from Dealer Computer Services Inc., another Reynolds and Reynolds subsidiary. Brockman also gave more than $280,000 to Perry during his statewide races in Texas over the past decade, according to contribution files posted by the Texas Tribune.

Another top Restore donor was Rocco Ortenzio, who gave $750,000 to the committee. Ortenzio, who previously gave $250,000 to Romney, heads a Pennsylvania-based health care empire that includes private hospitals, rehab centers and clinics. Ortenzio has given to numerous Republican and Democratic officeholders, but donated regularly to Romney rival Rick Santorum when he served in Congress.

The filings show a $500,000 donation to the pro-Romney group by a first-time contributor, Warren Stephens, an Arkansas investment banker. And $67,500 was donated by another new Restore donor, Richard Mellon Scaife, a longtime conservative fundraiser who publishes the Pittsburgh Tribune-Review. Scaife has funded conservative and libertarian causes for decades and aided conservative efforts to impeach former President Bill Clinton in 1998.

There were also new large donations to Restore from several prominent Romney supporters who previously funded the super PAC. William Laverack, a New York investor who previously gave the committee $350,000, added another $150,000 in April. Like Conard, Laverack had masked an earlier $200,000 contribution through a Connecticut limited liability corporation called Paumanok Partners. And two Florida super PAC contributors, developer H. Gary Morse and his wife, Renee, each gave $100,000 to Restore in May. That $200,000 figure added to $500,000 donated previously to the committee by Morse's wife and the Florida retirement community he runs, Villages of Lake Sumter.

The pro-Romney committee's roster of veteran GOP fundraisers was matched in May by Rove's super PAC, whose funders included some donors who have given copiously to both groups. According to filings released by Rove's committee late Wednesday night, Alliance Coal President Joseph Craft gave $1.25 million to American Crossroads in May after donating $500,000 to the pro-Romney super PAC. And Crow Holdings LLC, a holding company tied to Texas businessman Harlan Crow, gave American Crossroads $1 million in May after previously handing over $300,000 to the pro-Romney committee.

The super PAC supporting Obama showed new signs of life after months of subsistence funding. The group posted three donations of $1 million -- from Houston personal injury trial attorney and longtime Perry foe Steve Mostyn, from Washington, D.C., developer and veteran Democratic Party insider Franklin Haney and from south Florida philanthropist Barbara Stiefel.

Meanwhile, Obama's national campaign reported $109.7 million in the bank at the end of May but spent more than it took in during the same period. The campaign collected $39.1 million and spent $44.5 million during the month. The Democratic Party, meanwhile, had $29.6 million cash on hand at end of the month, raising about $20 million during the period and spending $14.6 million.

Even as it has drawn even with Obama's financial strength, Romney's campaign is taking few chances at being outspent. His national finance team is hosting a retreat in Utah this weekend for contributors who raised tens of thousands of dollars for his campaign. GOP heavyweights like former Florida Gov. Jeb Bush and former Secretary of State Condoleezza Rice are expected to attend.