President Barack Obama and Mitt Romney Wednesday girded for an epic White House clash after the Republican took a huge step towards his party nomination with a crushing Florida primary win.

Romney's victory over Newt Gingrich restored him as the hot favorite to head the Republican ticket in November's election, and revived the prospect of the showdown with the Democratic president that the Obama camp has always expected.

The former Massachusetts governor had trained his fire not on his Republican rivals but directly on Obama in his victory speech on Tuesday night, driving home the narrative that only he could restore America's historic mission.

In a victory lap on US television morning shows, Romney turned to Obama's economic record, charging the president had raised taxes, choked businesses with regulation, refused to tap US energy sources and "let China run all over us."

"This president does not understand how this economy works and I do, because I spent my life in the economy," Romney, a former venture capitalist, told CBS.

"I'll open up markets for our goods, get our energy, get regulation right, and get taxation right."

The Obama campaign quickly hit back, arguing that a toxic Republican nominating melee was weakening Romney's general election prospects.

Senior strategist Stephanie Cutter argued that Romney's Florida victory had come at a "steep price" -- not just in terms of the $15 million he and allies reportedly splashed on a fearsome negative advertising blast at Gingrich.

"Second, and more ominously for Romney, his unprecedentedly negative, far-right Florida campaign continued to damage him among the swing voters he would need in November," Cutter wrote in a campaign memo.

Recent polls of the vital swing voting bloc support the view that Romney would benefit by ending the bitter Republican race as soon as possible.

An ABC News/Washington Post survey last week showed that Romney's unfavorable rating among independent voters climbed to 51 percent while his favorable rating fell to 23 percent.

Obama, though, has his own problems with independents, a majority of whom backed his 2008 presidential campaign: a New York Times/CBS poll last month put his approval rating with the key bloc at 31 percent.

Romney flew to Nevada to campaign ahead of Saturday's caucuses, but sparked a new controversy which betrayed his propensity for generating headlines bad for his campaign.

In a CNN interview, Romney served up a sound bite -- "I'm not concerned about the very poor" -- which is sure to be used in attack ads and plays into a narrative that he is an uncaring, out of touch multi-millionaire.

In the full quote, Romney says that the poor can take advantage of a social safety net which he will fix, that he does not care for the rich either but is most worried about the economic plight of the middle classes.

But Romney's enemies are certain to rip the comment out of that context in the vibrant heat of a presidential election.

On a happier note for Romney, his Florida win demonstrated his ability to run a well drilled and funded statewide campaign and shrewd targeting of key territory in central Florida which is home to most of the state's swing voters.

Florida has 29 of the 270 electoral votes needed to win the presidency and, given how the political map is shaping up, is a must-win for Romney if he is to capture the White House.

Obama has uncertain prospects in the state, given an unemployment rate of nearly 10 percent and a tsunami of mortgage foreclosures which have hammered the savings and security of the middle class.

The president could lose Florida and still win the presidency, according to most projections, but his margin of victory would be considerably narrowed, leaving cliffhanger races in other swing states even more crucial.

A Quinnipiac University poll last week showed Obama and Romney locked in a tie in the state. Recent national general election polls show Obama with a lead of only a few points over the Republican.

Obama knows that barring a surprise explosion of growth, he will probably lose November's election if it becomes a referendum on his economic record, so he is trying to frame an alternative narrative for voters.

He appeared in Virginia, another swing state, Wednesday, touting a new plan to allow responsible homeowners to refinance underwater mortgages, and took a veiled swing at Romney, seizing on comments by his likely foe that housing market should be allowed to hit "bottom."