President Obama had 10 times as much cash on hand at the end of March as GOP rival Mitt Romney, underscoring the steep financial challenge facing the presumptive Republican nominee as the general election campaign begins in earnest.

Obama on Friday reported a cache of $104 million in a monthly filing with the Federal Election Commission, compared with $10.1 million in the bank for Romney as of March 31. Obama’s campaign raised $35 million during the month while Romney took in $12.6  million, the filings show.

The disclosures illustrate a key obstacle confronting Romney as he pivots from a hard-fought and potentially damaging GOP primary to directly face the Obama campaign juggernaut, which has raised more than twice as much money and has been able to stockpile funds in preparation for November.

One major bright spot for Romney comes from conservative super PACs and other independent groups, which are not restrained by campaign-finance limits and outraised both Romney and the Republican National Committee in the early months of the year.

The pro-Romney Restore Our Future super PAC spent nearly $13 million in March helping Romney knock back a challenge from former senator Rick Santorum (Pa.), who spent $6 million and dropped out of the race earlier this month. American Crossroads, a conservative group founded with the help of GOP strategist Karl Rove, raised $49 million in the first thee months of the year, much of it from anonymous donors giving to its nonprofit arm.

That puts Crossroads ahead of Romney’s campaign — which reported raising $31.2 million in the same period — and the Republican National Committee, which brought in $44 million, records show. Crossroads and other independent groups are expected to spend hundreds of millions of dollars attacking Obama over the next 6-1/2 months.

The new figures underscore the expanded influence of Crossroads and other independent groups, which have been freed by court rulings to raise unlimited funds from individuals and corporations.

The amount raised in March by Romney pales in comparison to the $53 million brought in by Obama and the Democratic National Committee, but Romney has stepped up his fundraising dramatically since Santorum bowed out of the race.

The Romney campaign viewed the numbers as positive and said they were in a good position to challenge Obama. “Mitt Romney’s continued strong fundraising shows that voters across the country are tired of the failures from President Obama,” finance chairman Spencer Zwick said in a statement. “We will continue the hard work to raise the necessary funds to defeat President Obama and change the direction of the country.”

Despite a hard-fought primary contest, Romney’s fundraising has lagged compared with 2008, though his finances that year were bolstered by a personal loan of more than $40  million. Romney, a wealthy former private equity manager, has not contributed any of his own money to the campaign this time around.

Obama and the DNC have raised a combined $359 million since he launched his reelection effort, including $197 million for the president’s campaign. Obama had raised about $240 million by this time four years ago, according to data from the Campaign Finance Institute.

Obama continued to draw more heavily from small donors than Romney, who collected nearly 90 percent of his money in March from contributors giving more than $200 and has a large proportion of wealthy donors who have given the maximum of $2,500 during the primary, reports show.

“People are building this organization five and ten bucks at a time to take on Mitt Romney,” Obama campaign manager Jim Messina said earlier this week.

Many of the wealthiest donors are contributing to super PACs, particularly on the conservative side.

Restore Our Future took in $8.7 million last month, including $850,000 from Chicago financier Kenneth Griffin; $1 million from a firm headed by Florida investor Bill Koch; and $500,000 from James Davis, chairman of the New Balance athletic shoe company. Davis also gave $500,000 to the group last year, leading to protests from gay rights activists.

Liberal super PACs have had little success matching their conservative rivals. Priorities USA Action, a super PAC formed by two former Obama aides, says it raised just $4.5 million from January to March.

The Obama campaign also released its list of more than 530 official fundraisers who help bundle together checks from friends and associates, including 117 people who have raised $500,000 or more. Romney has declined to release his own campaign bundlers, except for a handful of lobbyists who must be identified by law.

The Obama campaign said Friday that it had returned $50,000 raised by a New York supporter accused in court of defrauding a businessman, impersonating a bank official and dodging creditors.

Spokesman Ben LaBolt said the campaign returned a donation of $35,000 from the fundraiser, Abake Assongba, and another $15,000 from her husband, Anthony J.W. DeRosa. Assongba had been on the campaign’s public list of campaign bundlers earlier, but was absent from the updated list released Friday.

The Washington Post reported last month that Assongba was dogged by a collection agency and a court order to pay more than $10,000 in unpaid rent for her former Brooklyn apartment, among other issues. Assongba was also sued by a Swiss businessman in Florida who alleged being a victim of an e-mail scam. Assongba disputed the allegations.

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Photos: President Obama on the campaign trail