Super PACs and other groups dominated the race for the Republican presidential nomination last month, raising and spending tens of millions of dollars outside the traditional campaign system and playing a key role in extending an already tumultuous contest, according to new disclosures filed Monday.

One such political action committee backing Mitt Romney raised more than the candidate’s campaign in January, when it spent nearly $14 million on his behalf in the states that held early primaries and caucuses. The group, called Restore Our Future, leans heavily on six- and seven-figure donations from hedge fund managers and other investors.

Another super PAC helped keep Newt Gingrich’s rocky candidacy alive with $11 million in donations — although $10 million of that came from a casino magnate and his wife, the group’s Federal Election Commission filings show.

These and other FEC disclosures, which were due by midnight Monday, underscore the extent to which a small group of ultra-wealthy financiers and industry executives has come to dominate spending in the Republican nominating contest, a trend that seems likely to persist through the general-election campaign.

The success of Restore Our Future and other GOP-aligned independent groups prompted President Obama to shift course this month and endorse the aims of a super PAC dedicated to his reelection effort, which raised just $58,816 last month. Obama campaign officials say they fear they will be outspent by Republicans, and the operation’s January fundraising number — $11.8 million — suggests that he may not be able to match his record from 2008.

Two Republican candidates with less-robust super PACs — Rep. Ron Paul (Tex.) and former senator Rick Santorum (Pa.) — posted healthy totals for January, each raising $4.5 million. The numbers show that both are likely to have enough money to compete in the months ahead.

The figures are not far from the $6.5 million brought in by Romney, the top GOP fundraiser. Santorum’s fundraising figure preceded his rise in the polls, which has made him the biggest current threat to Romney.

But the largest amount of money is going to the super PACs. Restore Our Future has nearly a dozen donors who each have given $1 million or more since last year to support Romney, and many of those same contributors also help raise money for Romney’s formal campaign. The group is funding millions of dollars worth of attack ads against Santorum in Michigan.

A pro-Santorum super PAC — the Red, White and Blue Fund — reported raising $2.1 million in January, most of which came from two donors: $1 million from Louisiana energy executive William J. Dore and $670,000 from investor Foster Friess, who garnered attention last week with a remark about aspirin and contraception. The super PAC Endorse Liberty, which supports Paul, took in $1.7 million from PayPal co-founder Peter Thiel.

Super PACs can raise unlimited amounts from individuals, corporations or unions as long as they don’t coordinate with candidates on how to spend the money.

Texas millionaire Harold C. Simmons has directed $12 million to the conservative American Crossroads super PAC, which will participate in the presidential and congressional races, plus $1 million to help Gingrich and $100,000 to aid Romney.

Although Romney leads the other GOP candidates in fundraising, his January total suggests that he may struggle to keep up with the furious pace of spending he will need through the Super Tuesday contests on March 6. His campaign doled out nearly $19 million in January, eating up almost all the money he had on hand at the end of 2011, and the campaign and super PAC together spent more than twice as much as they took in.

In announcing the numbers, the Romney team highlighted the figure he has raised since joining the race — $63.5 million — and said it ended January with about $7.7 million in cash on hand.

“We are very pleased with the continued support we have received from Americans across the country who want to see real change in Washington,” said Spencer Zwick, Romney’s finance chairman. “We have exceeded our fundraising goals and are on track with spending plans.”

But the campaign’s January numbers underscore the importance of Restore Our Future to Romney’s chances. The bulk of the $6.6 million the group raised last month came from about two dozen donors who gave $100,000 or more, including three who donated $500,000 each: New York hedge fund manager Bruce Covner; Alliance Coal President Joseph Craft; and David Lisonbee, head of a Utah nutritional-supplements firm called 4Life Research.

Hotel executives Bill and Richard Marriott of Bethesda chipped in $250,000 each last month, bringing their combined total to the group to $1.25 million. About a dozen donors have given the PAC $1 million or more since last year.

Nearly a quarter of the money the group has collected has come from corporations, which are free to spend unlimited amounts on elections because of a 2010 Supreme Court ruling.

The group’s filings show that it had about $16 million in cash on hand at the end of January, part of which is helping Romney attempt to regain the lead from Santorum in his home state of Michigan.

Winning Our Future, a super PAC backing Gingrich, took in a pair of $5 million donations from casino mogul Sheldon Adelson and his wife, with less than $1 million from other donors, records show. It’s unclear whether Adelson will pump any more money into the super PAC to help Gingrich, whose standing has plummeted since he won the South Carolina primary on Jan. 21.