Conservative super PACs and other outside groups are helping Republicans close a yawning fundraising gap with President Obama, giving the eventual GOP presidential nominee a better chance at winning the money race by November, according to new disclosures Tuesday.

Obama’s fundraising has continued to outpace that of his Republican challengers, amassing four times as much cash on hand at the end of December as front-runner Mitt Romney, records show. Overall, Obama raised $224.6 million in 2011 for his campaign and the Democratic Party, easily eclipsing the combined hauls of the GOP candidates.

But fresh disclosures that began arriving Tuesday at the Federal Election Commission reveal a key advantage now available to Republicans: a constellation of conservative groups that can raise unlimited money to help make up the difference with Obama’s campaign, which must abide by federal contribution limits.

American Crossroads, a fundraising juggernaut founded with the help of GOP political guru Karl Rove, reported raising $51 million in 2011 for its super PAC and nonprofit arms, with a goal of raising about $200 million more by November. Other super PACs backing Republican presidential candidates raised tens of millions to spend in primary-election states, suggesting a deep reservoir of financial resources for the eventual nominee.

Interest groups have begun to hit Obama with millions of dollars’ worth of negative advertising. American Crossroads has spent $10 million on television ads against the president and Americans for Prosperity, another conservative group, has spent $6.8 million, according to data from Kantar Media/CMAG.

Obama began running his own television ads two weeks ago, but he is still being outspent by the Republican interest groups targeting him. In the week that ended Sunday, Americans for Prosperity spent $1.6 million on television ads attacking the Obama administration’s support of the bankrupt green-energy firm Solyndra. Obama’s campaign spent $1.3 million on television ads to defend his record on the matter.

The emerging pattern suggests that Obama may have an increasingly difficult time staying ahead of his competitors in the money race this year, particularly after Republicans coalesce around one candidate focused on winning the White House. That contender will almost certainly receive a surge of contributions from Republicans who want to beat Obama.

The president is likely to receive meager help from the main Democratic super PACs, which reported bringing in just $19 million in combined fundraising in 2011.

“There’s a great incentive on the side of wealthy conservatives to contribute in this election, given the desire to defeat the president and the perceived weakness of the president given the economy,” said Anthony Corrado, an elections expert at Colby College and former Democratic Party official.

American Crossroads President Steven Law agreed, adding that the power of incumbency gives Obama an edge over his rivals.

“The party that has Air Force One and the presidential podium has the advantage to raise more resources,” Law said. “The eventual Republican nominee will start from a position of financial and perhaps physical exhaustion.”

But Obama campaign spokesman Ben LaBolt said the preponderance of outside money on the GOP side suggests a lack of grass-roots enthusiasm for Romney and other candidates.

“Since Republican voters aren’t enthusiastic about the field and since the campaigns have no real ground game, the candidates relied on millions of dollars in outside spending to eviscerate their opponents,” LaBolt said of the early primaries. “There’s no doubt we’re going to have to lean heavily on our supporters across the country early and often this year to ensure that we’re as competitive as possible on the ground and on the air.”

Outside groups played a pivotal role the last time a president ran for reelection. George W. Bush raised $132 million for his campaign in 2003 and was sitting on almost $100 million in reserves. The eventual Democratic nominee, Sen. John F. Kerry (Mass.), raised $19.6 million from donors in 2003 and had $1.6 million on hand at the end of December, despite a sizable loan from his personal fortune.

But in the 2004 general election, liberal groups funded by wealthy Democratic donors came to Kerry’s aid, eventually spending hundreds of millions to attack Bush.

This year, conservative groups may have an even steeper hill to climb, given the track record of Obama, who shattered all records by raising $745 million in 2008. New FEC reports filed Tuesday showed that the president raised $68 million between his campaign and the Democratic National Committee from October to December and was sitting on $81.8 million in cash at the close of the year.

Nearly half of the money Obama collected came from contributions that were less than $200, a reflection of his longtime focus on grass-roots donors. But he also disclosed 445 “bundlers” concentrated in Hollywood, Silicon Valley and New York who raised $50,000 or more for him and the Democratic Party, accounting for at least $74 million in contributions.

Romney’s campaign, by comparison, says it raised $24 million and had $19 million on hand, much of which has been drained over the past month in a costly fight with Newt Gingrich and other GOP challengers in the early-primary states. Romney and other Republicans have declined to reveal their bundlers.

Romney has been helped by the super PAC Restore Our Future, which has reported spending $17.1 million on his behalf — including $10.7 million in Florida alone. The group reported raising $30 million, mostly from Wall Street and energy industry titans, with $24 million on hand at the end of December.

Gingrich, who had less than $1 million on hand at the end of December after counting debts, also has relied on a super PAC. The group, Winning Our Future, has collected $10 million from casino magnate Sheldon Adelson and his wife to pay for advertising in South Carolina and Florida.

Even lesser candidates are receiving a share of the large checks. Rep. Ron Paul (Tex.), who raised $13 million in the fourth quarter, is benefiting from a $900,000 donation from PayPal founder Peter Thiel to a super PAC to buy Internet ads boosting his candidacy. The group reported spending $3.3 million through Tuesday.

Texas Gov. Rick Perry — a former candidate who spent about $1,100 for each of the few votes he received in early contests — was propped up in part by a super PAC funded by some of his Texas constituents. Contran Corp. of Dallas, owned by billionaire Harold Simmons, donated $1 million to back Perry. Simmons and his company also gave $7 million to American Crossroads.

Former Utah governor Jon Huntsman Jr., who also left the race, benefited from $1.9 million in donations his father made to the Our Destiny PAC.