Mitt Romney’s supporters rallied in February to shore up his struggling presidential bid, giving a combined $18 million to his campaign and to a super PAC that is paying for a barrage of ads attacking his Republican challengers, according to new disclosures filed Tuesday.

The contributions included a $3 million check to the pro-Romney super PAC from Texas home builder Bob Perry, a prodigious conservative donor who gained national prominence in 2004 by helping fund the Swift Boat Veterans for Truth attacks on Democratic presidential nominee John F. Kerry.

The monthly disclosures, which were due by midnight at the Federal Election Commission, illustrate Romney’s continued financial advantage over challengers Rick Santorum and Newt Gingrich, even as he struggles to amass enough delegates to sew up the GOP nomination.

Romney’s campaign has said that it brought in $11.5 million in February and burned through a similar amount as he attempted to overcome losses to Santorum in Colorado, Missouri and Minnesota.

Santorum reported raising $9 million on the strength of those early February victories, with $2.6 million in cash and $922,000 in debts going into March.

Gingrich, meanwhile, continued to cope with the kind of serious financial problems that have dogged him since his campaign nearly imploded last year, reporting more debt — $1.5 million — than cash on hand at the end of February. He raised $2.6 million and spent $2.8 million, the report shows.

The main bright spot for Gingrich has been Winning Our Future, a super PAC supporting the former House speaker’s candidacy that raised $5.7 million in February — almost all from casino magnate Sheldon Adelson and his relatives. The Adelson family has given the group $16.5 million in total, records show.

While the Republican field continues to scrap for donors and delegates, President Obama reported raising a combined $45 million for his campaign and the Democratic Party, an amount that falls short of his 2008 pace but puts him far ahead of his potential 2012 competitors. The Obama campaign reported having nearly $85 million in cash on hand on Feb. 29, or about 12 times the amount of available money reported by Romney.

Santorum and an allied super PAC have been badly outgunned by pro-Romney forces, which outspent the former senator from Pennsylvania by seven to one ahead of Tuesday’s primary in Illinois.

Even so, Santorum came close to matching Romney’s campaign total in February by amassing a large number of smaller donations. His campaign also said Tuesday that it had great success in peddling the candidate’s signature gray sweater vests, which were offered free to donors giving $100 or more.

“The warmer temps make this difficult to believe, but the @RickSantorum campaign has sold more than 3,000 sweater vests,” spokesman J. Hogan Gidley wrote on Twitter on Tuesday.

The pro-Romney group, Restore Our Future, is the largest super PAC to emerge in the 2012 cycle, raising more than $40 million since last year and spending most of the money on attack ads. Super PACs can raise unlimited money as long as they refrain from directly coordinating their spending with candidates.

In February, the group collected $100,000 or more from 14 donors, including $500,000 from former Univision executive Jerry Perenchio, $500,000 from Missouri building-products executive David Humphreys and $100,000 from Griff Harsh, the husband of Romney booster and Hewlett-Packard chief executive Meg Whitman. Since last year, the super PAC has brought in $1 million or more from a dozen donors, led by Perry with $4 million.

The group also accepted more than $160,000 in donations last month from payday-lender interests, including South Carolina-based Advance America and a firm tied to Seattle-based Moneytree, records show.

Romney has vowed to overturn a Wall Street reform law that includes stronger oversight for payday lenders, which have been widely criticized by watchdog groups for issuing short-term loans at exorbitant interest rates.

Perry has contributed to many Republican causes over the years, including $4.45 million to the Swift Boat group in 2004 and nearly $10 million since 2010 to American Crossroads, a top GOP super PAC. He also contributed $100,000 to the main super PAC supporting Texas Gov. Rick Perry, who abandoned his presidential bid in January.

The Obama campaign is on track to fall short of its record $745 million fundraising haul in 2008 and has lagged in contributions from donors giving $2,000 or more. Nonetheless, it is far ahead of the GOP field and has reported contributions from more than 1.4 million supporters.

Obama’s February reports show that the campaign spent money at a much slower rate than in January, when it dumped millions into new and expanded offices around the country. That doesn’t mean expenses were low, however: For a pair of fundraisers in New York, the Obama Victory Fund reported spending $95,000 on catering and other costs at the upscale Daniel restaurant in Manhattan.

Staff writers Aaron Blake and T.W. Farnam contributed to this report.