Harlan Crow, the Texas construction magnate, gave $300,000 personally and through his company. William Koch, whose brothers Charles and David are among the country’s most prominent backers of conservative causes, gave $1 million personally or through Oxbow Carbon, the energy company he founded. Members of the Walton family, founders of the Walmart chain, gave over $200,000, while Bob Perry — a wealthy home builder who has long been the top patron of Mr. Romney’s erstwhile rival, Gov. Rick Perry of Texas — chipped in $500,000 in early December.

But as Mr. Romney sailed to an overwhelming victory in Florida’s primary on Tuesday night, fund-raising documents filed by President Obama showed the kind of financial juggernaut he will face if he becomes his party’s nominee: Mr. Obama reported raising a total of $140 million in 2011, far eclipsing the $57 million Mr. Romney raised for his campaign for the year.

The figures underscored the deep divide between how each party’s presidential contenders are financing their early bids for the White House: Mr. Obama exploiting the well-oiled machinery of an incumbent with a powerful grass-roots apparatus and hundreds of “bundlers” gathering checks of up to $2,500 per person from friends and associates, and his Republican opponents relying far more heavily on independent groups empowered by court decisions that have made it easier for wealthy individuals and corporations to spend unlimited amounts of money to intervene directly in election contests.

Newt Gingrich raised nearly $10 million in the final three months of 2011, and his spokesman, R. C. Hammond, said in a Twitter message that Mr. Gingrich had raised an additional $5 million in January, capitalizing on strong debate performances and the collapse of other Republican candidates.