By Alina Selyukh and Patrick Temple-West
WASHINGTON (Reuters) - Mitt Romney is struggling to regain control of the race for the Republican presidential nomination, but his allies appear ready to offer him a strong crutch for the road ahead.
Restore Our Future, the independent "Super PAC" that supports Romney, spent $13.5 million in January on ads attacking his rivals and still emerged with $16.3 million in the bank, according to disclosures filed Monday with the Federal Election Commission.
The pro-Romney PAC, or political action committee, spent $12.3 million alone on TV, Internet and radio ads that went after former U.S. House of Representatives speaker Newt Gingrich, Romney's chief rival at the time.
Challenging Gingrich's ethics and judgment, the ads helped propel Romney to victory in the Florida primary on January 31 and gave Gingrich a public relations problem from which he has not recovered.
Now, with Romney facing a new challenge from former Pennsylvania Senator Rick Santorum in the Michigan primary on February 28, Restore Our Future is spending another $7.7 million in several key states -- including Michigan, where the PAC has spent $1.8 million on ad spots.
Monday's filing with the FEC showed how the pro-Romney PAC is still the leader in a new era of campaign spending, in which independent groups can raise and spend unlimited amounts of money to try to boost or tear down candidates.
Last month alone, Restore Our Future raised $6.6 million, more than any of its candidate-boosting rivals raised in all of 2011.
Individual donations to campaigns are limited to $2,500 during the nomination season and another $2,500 for the general election. The absence of such limits on PACs has allowed the very wealthy to use such groups to try to influence the campaign and the elections.
Through PACs, Republicans also could make up the disparity between their campaign fundraising and that of Democratic President Barack Obama's campaign for the November 6 election.
Obama's campaign reported on Friday that it raised $29.1 million in January, which followed a three-month period in which Obama and Democrats backing him raised more than $68 million.
The pro-Romney PAC has received donations of $1 million or more from at least nine contributors, plus other large donations from the former private equity executive's friends in the investing world.
Contributors included prominent former hedge fund managers Julian Robertson, Paul Singer and John Paulson as well as Houston homebuilder Bob Perry.
Two Utah-based firms with a shared address and ties to former Nu Skin executives, F8 LLC and Eli Publishing, each gave $1 million.
In January, the ranks of donors also were joined by Harold Simmons, a billionaire Dallas banker who along with his company has given more than $7 million to American Crossroads, a PAC that supports Republican presidential and congressional candidates.
Simmons gave $100,000 to Restore Our Future. Alongside Bob Perry, Simmons had previously supported Texas Governor Rick Perry in his failed presidential bid.
In 2004, the duo gave millions of dollars to Swift Boat Veterans for Truth, a group that helped undermine Democratic presidential nominee John Kerry by attacking his Vietnam War record.
Restore Our Future also has received $750,000 each from brothers J.W. Marriott Jr. and Richard Marriott, of the international hotel chain.
Romney, a former Massachusetts governor, seemed on his way to winning the state-by-state nomination race after taking Florida's primary. But after winning contests in Minnesota, Missouri and Colorado, Santorum jumped back into contention in the battle for the right to face Democratic President Barack Obama in the November election.
Santorum now leads most polls in Michigan, where Romney grew up as the son of an auto executive and Michigan governor. With 10 state contests looming on "Super Tuesday," on March 6, Romney is desperate to recapture momentum in the race.
Restore Our Future, in step with Romney's campaign, has now turned its attacks toward Santorum, who likely will be the subject of most of the PAC's ads in the coming weeks.
The FEC filing deadline for January fundraising and spending is midnight Monday EST (0500 GMT on Tuesday).
PACs supporting Santorum and Gingrich had not filed their January reports with the FEC as of 5:20 p.m. EST Monday (1020 GMT). The campaigns of all four Republican contenders -- Romney, Santorum, Gingrich and Texas Congressman Ron Paul -- also had not filed.
(Additional reporting by Alexander Cohen; Editing by David Lindsey and Christopher Wilson)