After days of often bitter campaigning, Republican voters in Florida are choosing their favorite candidate to run for president.

Former Massachusetts governor Mitt Romney expressed confidence before voting started. The Florida Republican primary election Tuesday comes just over a week after he was soundly defeated in the South Carolina primary.

Strong debate performances and heavy advertising that attacked Romney's top rival – former House speaker Newt Gingrich – helped Romney surge in the polls. Recent opinion polls show Romney has a double-digit lead over Gingrich in Florida. Romney's campaign has taken on a confident tone.

“Speaker Gingrich, he's not feeling very excited these days. I know. It's sad. He's been flailing around a bit.”

But Gingrich, who trailed in the polls for months last year, only to surge to a big win in South Carolina, vows that his campaign will not end if he loses in Florida.

“We're just getting started.”

Florida is one of the biggest states, and the winner here not only garners more delegate support for the Republican national convention later this year, but his campaign may draw in new backers in other states.

The delegates officially nominate the candidate to face Democrat Barack Obama in the November presidential election.

Former U.S. senator Rick Santorum and Texas congressman Ron Paul are the two other candidates on the ballot in Florida, although polls show both far behind the frontrunners.

During the Florida campaign, Gingrich lashed out at Romney, accusing him of being a liberal and running dishonest political ads. The former congressman says he expects a long campaign in the battle for the Republican presidential nomination.

Romney has said that Gingrich is making excuses for his debate performances, and blasted Gingrich for being found guilty of ethics violations that forced him to resign as House speaker.