Media playback is unsupported on your device Media caption Mitt Romney, Newt Gingrich, Rick Santorum and Ron Paul, each stated their determination to become the Republican candidate to take on President Obama

US presidential hopeful Mitt Romney has won a resounding victory in the Republican primary election in Florida, according to official results.

Mr Romney polled 46%, but rival Newt Gingrich, who only managed 32%, says he has no intention of dropping out.

Florida's primary was the biggest of the 2012 election season so far and saw a bitter TV ad battle between the men hoping to take on Barack Obama.

Exit polls indicated the economy was the key issue for a majority of voters.

The data suggested Mr Romney led his main rival on a host of issues - including likely handling of the economy.

The exit polls also suggested he appealed to a broad range of Florida Republican voters, including the state's crucial Hispanic population.

'Get out of the way'

Mr Gingrich narrowly won the support of evangelicals and pro-life voters, but saw Mr Romney win the backing of a majority of Tea Party sympathisers.

Analysis This victory proved some of the truths strategists prefer to speak behind closed doors, not on cable TV. Money matters. Negative works. Go for the kill. Mitt Romney proved himself quite an operator. He crushed Newt Gingrich with a series of very negative TV adverts, attacking the former speaker's character and suitability to be president. He showed some fire in the debate. But above all this came down to money. He spent at least $16m in Florida in the last month alone. He put out 13,000 TV ads. Gingrich had around 200. By contrast Newt Gingrich pulled his punches in the debates, tried to be presidential and just didn't make much impact. He drew back, to an extent, from attacking the way Romney made his money. There was no display of a killer instinct. Read more from Mark

Fellow candidates Rick Santorum and Ron Paul are also seeking to become the Republican nominee and challenge Mr Obama in November's general election.

Neither candidate campaigned hard in Florida, and they gave their election night speeches from Nevada, where the next contest takes place on Saturday.

Mr Santorum finished third in Florida, with 13%, and Mr Paul fourth with 7% of the vote.

A victory for Mr Romney in the Sunshine State gives him his second win, after the New Hampshire primary, and sees him claim all of Florida's 50 nominating delegates.

A total of 1,144 delegates are needed for a candidate to win the Republican nomination.

Addressing his supporters after his win, Mr Romney promised to offer a "winning ticket for America" at the general election in November.

"A competitive primary does not divide us, it unites us and we will win," said Mr Romney, paying tribute to his three opponents in Florida.

He challenged President Obama on his record on the economy and unemployment, telling him: "Mr President, you were elected to lead, you chose to follow, and now it's time to get out of the way."

"My leadership will end the Obama era and begin a new era of American prosperity," he said, to cheers and applause.

He promised that if he won power he would rein in government spending, balance the national budget, and take action to repeal Mr Obama's healthcare law.

Gingrich defiant

Mr Gingrich remained defiant, speaking to his supporters without a teleprompter and insisting he would remain in the race until the very end.

A sign at his election night party seemed to sum up the Gingrich attitude, reading: "46 States to go".

"It is now clear," Mr Gingrich said, "that this will be a two-person race between the conservative leader Newt Gingrich and the Massachusetts moderate."

And in a critique of the high-powered ad campaign launched against him in Florida, he added: "We're going to have people power defeat money power in the next six months."

Rick Santorum, the former Pennsylvania senator who came in third, said Newt Gingrich "had his opportunity" in Florida after a big win in South Carolina 10 days ago but had blown his chance to be the alternative to Mr Romney.

Mr Gingrich's personality and record had become the issue, Mr Santorum said, something that would not help the Republicans in the long run.

He also criticised the negative tone of the Florida campaign, saying Republicans would not beat Barack Obama by "mudslinging".

"We can do better than the discussion and the dialogue that were going on in the state of Florida," he said.

Fourth-placed Ron Paul hailed his vocal supporters in Nevada and said he would battle on through the upcoming mountain state caucuses.

US politics glossary Use the dropdown for easy-to-understand explanations of political terms: Air war Air war The battle between candidates to get as much advertising on television and radio as possible. In recent years, online adverts, which are cheaper and can be more carefully targeted, have grown increasingly important.

"The message of this election is loud and clear... that we want more freedoms back and we don't want more government," said Mr Paul, a strident advocate of smaller government.

Mr Romney, 64, has been the front-runner for much of the race, but was thrashed by his rival in South Carolina's primary earlier last month.

The former governor then overturned his rival's lead after two muscular debate performances and a blitz of attacks.

Mr Romney and his allies pumped more than $16m (£10m) into Florida TV advertising, mainly attacking Mr Gingrich, whose campaign and supporters could only spend about $3m in reply.

The Romney campaign has sought to portray Mr Gingrich as an erratic, Washington influence-peddler.

Mr Gingrich, 68, a former Georgia congressman, has accused Mr Romney - a private equity tycoon and one of the richest ever US presidential candidates - of being a closet liberal who is trying to buy his way to the White House.

Mr Romney has a better-funded campaign, a superior national organisation and the backing of much of the Republican establishment. A series of polls has indicated he stands the best chance of beating Barack Obama.

But he has struggled to dispel misgivings among some conservatives about his Mormon faith and political record as governor of a liberal state.

In the past, Mr Romney has switched stances on abortion, gay rights and gun control, and passed a healthcare reform in Massachusetts that was the template for President Obama's overhaul of the system nationally.