Mitt Romney has won the Republican primary in Florida, soundly defeating his main rival Newt Gingrich and taking a big step towards challenging US President Barack Obama in November's election.
With his win on Tuesday in the largest nominating contest so far, Romney regained the political momentum he had lost after Gingrich's victory in the South Carolina primary and set his sights squarely on the incumbent president in a victory address to supporters.
"As this primary unfolds, our opponents in the other party have been watching, and they like to comfort themselves with the thought that a competitive campaign will leave us divided and weak," Romney told a jubilant crowd.
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"But I've got news for them. A competitive primary does not divide us. It prepares us, and we will win," he said.
Attacking Obama, he said: "Mr President you were elected to lead, you chose to follow, and now it’s time for you to get out of the way."
The win gives Romney, a former Massachusetts governor, all 50 of Florida's delegates to the Republican National Convention in August. A candidate needs at least 1,144 delegates to become the nominee.
Gingrich, the former speaker of the House of Representatives, has vowed to fight on regardless of Tuesday's vote.
"It is now clear that this will be a two-person race between the conservative leader Newt Gingrich and the Massachusetts moderate," Gingrich said, refering to Romney.
The next contest is the Nevada caucuses on Saturday, followed next Tuesday by caucuses in Colorado and Minnesota and a primary in Missouri.
Analysts said the margin of victory in Florida, 46 per cent to 32 per cent with 96 per cent of the roughly two million votes counted, cemented Romney's status as frontrunner in the race.
Two other candidates, the former Pennsylvania senator Rick Santorum and Texas Congressman Ron Paul, garnered 13 per cent and seven per cent of the votes respectively.
The win also demonstrated Romney's ability to compete strongly in a major political battleground state with a broad voter base including Tea Party conservatives, evangelical Christians and Cuban-Americans.
According to exit polls by CBS, 62 per cent of the Republican voters said the economy was the most important issue to them. Romney has campaigned hard on his credentials to fix the economy based on his experience as a businessman.
Voters also said in exit polls that they were very concerned about picking a candidate who could beat Obama.
Al Jazeera's Alan Fisher, reporting from Tampa, Florida, said: "If you look at the next six contests, four of them certainly favour Mitt Romney. He has advantages in opinion polls in each of those states."
"So, he is pushing forward believing that winning in Florida has given him a significant advantage in hunting down the Republican nomination," he said.
Our correspondent said that Gingrich appeared to be struggling in terms of fundraising and campaign organisation.
"The problem Newt Gingrich has got is that, to a large degree, he did not expect to be still in the race at this stage.
"Gingrich knows he has got to do well in Nevada and if he doesn’t do well in the caucuses there, his campaign could be fatally damaged."
The voting came after a week of brutal campaigning that saw Romney and Gingrich exchange a barrage of negative and increasingly personal attacks.
Gingrich picked up the endorsement on Saturday night of former rival Herman Cain, who dropped out of the Republican race in December after allegations of sexual harassment and an extramarital affair.
Some analysts suggest Gingrich could fight on if he can persuade Santorum to quit the race, pushing more conservative Republicans towards the Gingrich camp, but Santorum has resisted calls for him to drop out of the contest.