Republicans are voting in Florida in what is expected to be a pivotal contest in the race for the party's presidential nomination.

More than 600,000 Floridians have already cast ballots in early voting leading up to this primary day.

A recent public-opinion survey indicates former Massachusetts governor Mitt Romney holding a 14-percent lead on his closest rival, former House speaker Newt Gingrich.

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.

The candidates are vying for Florida's 50 delegates to the Republican Party National Convention in August. The delegates' votes officially nominate the candidate to face Democrat Barack Obama in the November presidential election.

Both Romney and Gingrich have campaigned hard in the state, with the Romney campaign putting nearly $14 million into television ads against Gingrich. The candidates have also taken their criticisms of each other on the campaign trail.

Gingrich lashed out at Romney on Monday, 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.

Romney needs a win in Florida to regain his momentum after losing to Gingrich by double-digits in the South Carolina primary January 21.