TAMPA, Fla. -- Mitt Romney rolled to victory in the Florida primary Tuesday, dispatching an insurgent threat from Newt Gingrich and reclaiming his dominant position in the race for the Republican presidential nomination.

The commanding win offered a forceful response to the concerns that were raised about Romney's candidacy only 10 days ago after a stinging loss to Gingrich in the South Carolina primary. It also raised new questions about whether Gingrich can persuade Republicans of his electability.

"I stand ready to lead this party and to lead this nation," Romney told supporters Tuesday, urging Republicans to remain united and to focus on the party's goal of defeating President Barack Obama.

The outcome of the Florida primary promised to reorder the rest of the Republican field. Sensing vulnerability in Gingrich, Rick Santorum began running an advertisement in Nevada and Colorado comparing Gingrich's positions to the dual Democratic villainy of Rep. Nancy Pelosi, D-San Francisco, and Obama, saying his support for policies including the Wall Street bailout was "a slap in the face to the tea party."

The victory by Romney, which was built by a diverse coalition of the Republican electorate, allowed him to return to the hard job of pulling together a divided party and begin anew his argument that he has the best chance to beat Obama. Yet Gingrich indicated that he was staying in the race, with a "46 states to go" sign hoisted at

his election night party in Orlando.

Yet advisers to Romney pointed to his success here as a harbinger of his strength in a general election challenge against Obama. No state where Republicans have competed this year is more reflective of the nation's geographical, political and ethnic diversity than Florida, and its complexity seemed to help Romney to turn back the grass-roots coalition that Gingrich had been counting on.

"Primary contests are not easy, and they're not supposed to be," Romney said in his victory speech. "Our opponents in the other party have been watching and they like to comfort themselves that a competitive primary will leave us divided and weak. A competitive primary does not divide us. It prepares us, and we will win."

Romney's support in urban areas with concentrations of affluent and retired Republicans was enough to overcome tea party supporters, evangelicals and self-described "very conservative" voters who have generally coalesced around Gingrich -- although he also seemed to gain strength among tea party supporters.

The night also raised questions about Gingrich's strength moving forward. If there was one part of the state with a countermessage, it was its northwestern panhandle, which resembles the nation's South. Gingrich and Romney won equal support there, according to surveys of voters leaving polling stations -- giving hope to Gingrich for the coming Southern contests and pause to Romney, who struggled for traction in South Carolina.

After spending the week under intensive attack from Romney and the forces supporting him, Gingrich was entirely stripped of the momentum he had when he arrived here from his victory in South Carolina. Surveys of voters leaving polls found that he had the same percentage of tea party supporters, evangelical or very conservative voters that he had in South Carolina, roughly 4 in 10 -- but, in a state like Florida, it was not enough to even put him close to Romney.

The victory was the first for Romney that came without an asterisk.

The narrow advantage he appeared to have the night of the Iowa caucuses was overturned two weeks later in the certified results. His New Hampshire win was discounted by his Republican rivals because he was seen as a favorite son from a neighboring state.

But his commanding finish in the Florida primary, which drew more voters than the first three contests combined, represented an extraordinary turnaround for his prospects of winning the party's nomination. The outcome of the race, his advisers argued, should ease the qualms among some Republicans that he is not sufficiently conservative.

It was a winner-take-all primary, so the victory gave Romney 50 delegates. Yet Romney remains only a fraction of the way toward accumulating the 1,144 delegates needed for the nomination.

When Romney's aides were confident enough of a victory to discuss the landscape beyond Tuesday night, they started deliberating over what could best be described as their "Newt containment strategy." It is the delicate task of keeping one foot firmly planted on his back and the other free to move toward an anticipated general election battle with Obama.

Advisers to Romney have made it clear that they take seriously Gingrich's promise to stay in the race until the nominating convention that takes place here in August, given the persistence he has shown throughout the campaign.

But containing him will require a delicate balance between giving him too much -- or too little -- attention at any given moment.

The fast-approaching lull in the campaign -- with no debates scheduled until Feb. 20 and a 17-day break after the caucuses next week in Colorado and Minnesota -- is not expected to help Gingrich's lesser financed campaign. He has been sustained by the free attention he has drawn in debates and the news coverage of upcoming election nights.

And Romney's aides say they know that to attack him regularly during such slack periods could simply give him the oxygen of conflict to help him raise money.

Yet they also ignore him at their own peril, having twice presumed him politically dead only to see him rise up against Romney again.

Though never saying it outright, Romney has hinted that he believes the time is soon coming for Gingrich to give up his campaign, saying at one point this week that it was time for Gingrich to "look in the mirror" and accept the fact that his candidacy was no longer resonating.

"I would like to spend more of our time focusing on President Obama," Romney said Tuesday. "That's ultimately what's going to be essential to taking back the White House, but I'm not going to stand back and allow another candidate to define me."

But Romney's aides acknowledge that the normal pressure campaign -- such as calling upon donors of Gingrich to convince him to drop out, or pressing the candidate to do so for the good of the party -- will not likely work because Gingrich has positioned himself as running against the Republican establishment.

The focus of the contest was already shifting to Nevada.

Paul, whose strategy is built on a strong showing in caucus states where grass-roots organizing is easier, scheduled a "Florida Election Night Party" more than 2,000 miles away at a resort in Henderson, Nev., just outside Las Vegas.

Romney's campaign aides said they were also not content to ignore Santorum, who barely competed here, in part because his daughter had a hospital emergency in Pennsylvania that forced him to leave the campaign trail. But his campaign manager, Michael Biundo, said the campaign had also made a strategic decision to pull out of Florida given its expense and its winner-take-all delegate allocation.