One of Mitt Romney’s strongest assets as the GOP presidential front-runner is also a potentially serious liability in the race: his heavy reliance on a small group of millionaires and billionaires for financial support.

A quarter of the money amassed by Romney’s campaign and an allied super PAC has come from just 41 people, each of whom has given more than $100,000, according to a Washington Post analysis of disclosure data. Nearly a dozen of the donors have contributed $1 million or more.

The preponderance of mega-rich supporters poses a political challenge for Romney, who has struggled for weeks over questions about his vast wealth, his history as a private equity manager and a series of gaffes that seemed to highlight his privileged station. He stumbled again on Wednesday when he told a CNN interviewer that he was “not concerned about the very poor, because they have a safety net.”

Some of Romney’s biggest supporters include executives at Bain Capital, his former firm; bankers at Goldman Sachs; and a hedge fund mogul who made billions betting on the housing crash. These and other donor details follow the release last week of Romney’s tax returns, which showed millions held in the Cayman Islands and other overseas havens and a tax rate that is far lower than that paid by most American workers.

The revelations come at a time when President Obama and other Democrats are increasing their focus on economic fairness issues ahead of the 2012 elections, including calls to increase tax rates on millionaires and close tax loopholes on investment income. Sen. Al Franken (D-Minn.) said at a news conference Wednesday that hedge-fund managers are helping Romney because he opposes higher tax rates for a type of investment income, known as “carried interest,” that primarily benefits the wealthy.

“Of course these guys are going to give a million dollars,” Franken said. “What a bargain — what a bargain to give that to a candidate who they know will veto a bill that makes the carried interest subject to the top” income tax rate.

Romney spokeswoman Andrea Saul objected to such criticism and said 84 percent of the campaign’s donations in the fourth quarter last year were $250 or less. Meanwhile, the candidate sought to clarify his remarks to CNN about the poor, saying they were taken out of context.

“Wealthy people are doing fine,” Romney said. “But my focus in the campaign is on middle-income people. Of course I’m concerned about all Americans — poor, wealthy, middle-class — but the focus of my effort will be on middle-income families who I think have been most hurt by the Obama economy.”

The president has acquired nearly half of his campaign war chest from small-money donors, raising more from contributions of $200 or less than the Romney campaign has brought in overall, disclosure data show. Romney’s GOP rivals also have raised a larger proportion of their money from small donors.

Paul Begala, a longtime Democratic strategist who advises a pro-Obama group called Priorities USA, argues that Romney’s close connections to the super-rich exacerbate his problems relating to regular voters. Romney has generally fared poorly among lower-income voters in early GOP contests, particularly in his loss to Newt Gingrich in South Carolina on Jan. 21.

“He is of the rich, by the rich and for the rich,” Begala wrote in an e-mail. “He is Thurston Howell III: born rich and getting richer every day. . . . Mitt’s policies would definitely favor the over-privileged, and monarchs don’t start revolutions.”

GOP strategist Ed Rogers, who has not endorsed a candidate in 2012, said Romney’s stereotype as “a rich, detached banker” will have to be “managed, not solved.”

“Eventually, Romney’s private-business experience should be a net plus after having to watch Obama struggle with on-the-job-training and displaying no clue about how the private economy works,” Rogers said.

An Obama campaign spokesman declined to comment about Romney’s donors.

The president has plenty of wealthy benefactors as well, including 445 “bundlers” who have raised $50,000 or more for his reelection effort, stacked heavily with money from Hollywood, Silicon Valley and New York. The Priorities USA super PAC also has collected a handful of large donations from heavyweights, including $2 million from Dreamworks chief executive Jeffrey Katzenberg — a top Obama bundler — and $100,000 from movie director Steven Spielberg.

Romney has declined to name his bundlers, except for those required to be identified by law because they are lobbyists. But the roster of donors to a pro-Romney super PAC called Restore Our Future offers a revealing guide to some of his biggest financial supporters.

Ten donors to Restore Our Future gave $1 million to the group last year and another gave $2 million, accounting for 40 percent of the group’s $30 million in donations. The group’s treasurer declined to comment.

Four of the $1 million donors are New York-based hedge fund managers: Paul Singer, founder of Elliott Management; Robert Mercer of Renaissance Technologies; Julian Robertson of Tiger Management; and John Paulson, founder of Paulson and Co., who famously made $5 billion in one year by betting on the mortgage crisis.

If Romney becomes the GOP nominee, he will benefit from other Republican-aligned groups that have begun to attack Obama. One such group, American Crossroads, raised $51 million in 2011, including $7 million from Dallas billionaire Harold Simmons and his firm, Contran.

Romney’s super PAC has received a greater share of money from corporate coffers than his competitors have. The PAC reported raising $8.4 million from corporations in 2011, about 28 percent of its total fundraising.

Consol Energy, an $8 billion company publicly listed on the New York Stock Exchange, gave $150,000 to Restore Our Future. The company’s chief executive is J. Brett Harvey, a member of Romney’s Pennsylvania finance committee.

“It is common practice for CONSOL Energy to support political candidates that share a similar philosophy as it relates to a domestic energy policy,” the company said in a statement, adding that “Mitt Romney has articulated and embraced such an approach.”

Staff writer Paul Kane contributed to this report.