MIAMI // With a comfortable victory in Florida, Mitt Romney is closer to securing the Republican Party's nomination to challenge Barack Obama for the US presidency in November.
The former Massachussets governor's rivals remain unbowed, however. Newt Gingrich, Ron Paul and Rick Santorum have all vowed to stay in the race as it moves west. Their goal is to pick up as many delegates as possible in the eight caucuses and primaries scheduled before Super Tuesday - the March 6 vote that takes place simultaneously in 10 states.
A candidate must get 1,144 out of 2,288 delegates to win the party nomination. Mr Romney has secured 84 delegates, Mr Gingrich, the former speaker of the US House of Representatives, 27, Mr Paul, the Texas congressman, 10 and Mr Santorum, the Pennsylvania senator, has eight.
The Florida win was nevertheless a big moment for Mr Romney. Not only did he prevail in the largest and most diverse state to have voted so far, he did so with a double-digit margin and he came from behind.
Florida was a "tie-breaker", said Susan McManus, professor of political science at the University of South Florida. The Republican Party had moved its primary in Florida up in the schedule, she pointed out, specifically to test candidates to see if they can successfully "manoeuvre through a diverse group of voters".
She said: "That is exactly what Romney did. [Victory in Florida] made South Carolina seem like an outlier, an anomaly, the exception rather than the rule."
Mr Romney also spoke like he had the nomination already won on Tuesday night. He noted magnanimously his "three gentlemen" rivals as he turned his attention back to Mr Obama. He laid into the US president's record on the economy and promised to "build an America where hope is a new job and a pay check, not a faded word on a bumper sticker".
The contrast could not have been greater with Mr Gingrich. He came to Florida leading the opinion polls after his upset victory in South Carolina. But he performed uncharacteristically poorly in the two televised debates in Florida, and Mr Romney's greater financial muscle ensured that the airwaves here were flooded with negative advertising targeting Mr Gingrich's character, primarily his three marriages.
Those adverts have hit a nerve and there was an element of personal animosity in Mr Gingrich's concession speech on Tuesday in which he failed to congratulate Mr Romney on his victory.
"It is now clear that this will be a two-person race between the conservative leader, Newt Gingrich, and the Massachusetts moderate," he told supporters, a cynical use of the word "moderate". Labelling Mr Romney as a "liberal" has been a recurring theme in his campaign.
Mr Gingrich now needs to ensure that the momentum his campaign picked up by winning South Carolina does not completely fizzle out, said Chris Wilson, a Washington-based Republican pollster.
"The challenge for Gingrich is that he's got to show that he can raise money and be competitive. Otherwise he's going to be massively outspent in every state, and if he's vastly outspent in every state, he's never going to catch up."
In pictures: Mitt Romney take Florida primary
Mitt Romney, with superior spending power and a barrage of advertisements at his disposal, makes light of his opponents in the primary election in Florida.
Mr Wilson said Mr Gingrich was the only candidate able to challenge Mr Romney. As the signs brandished by supporters of Mr Gingrich on Tuesday night suggested, "46 states to go", the nomination process is still at its beginning.
"People want to say that this a defining moment for the campaign, but really what it is, is just another state," said Mr Wilson. "It's all a long way from being decided."
In a possible omen for Republican attempts to defeat Mr Obama, there was a lower turnout for this Florida primary then in 2008. Florida is a crucial swing vote and could well be decisive in November's presidential elections. But Republicans will need to energize voters in way they did not on Tuesday if they are to take the state back from the Democratic Party.
On Tuesday, outside one polling station at the North Shore Youth Center in Miami Beach, election officials were enjoying a warm afternoon and few voters.
The only voter during one half-hour stretch, Emilio Perez, 34, a shop owner, said he had voted for Mr Gingrich, "the other guy", because he wanted to send a message to the Republican Party that it should "act like a Republican Party". He did not, however, hold out much hope that Mr Gingrich had a chance of beating Mr Romney, or that Mr Romney or Mr Gingrich could seriously challenge Mr Obama. "I'm afraid not. I think Obama is a shoo-in."
