Florida's Republican voters go to the polls on Tuesday in a high-stakes presidential primary election, with former Massachusetts governor Mitt Romney holding a commanding double-digit lead in polls over rival Newt Gingrich.
Florida is the largest state to hold a presidential primary so far this year and a Romney victory would give him a big boost in the state-by-state battle to decide who will face President Barack Obama in the November election.
Polls opened at 7 a.m. and close at 7 p.m. local time. Most of the state is on Eastern Time (plus 5 hours GMT), except the western Panhandle region, which is on Central Time and where polls will close an hour later.
Gingrich, a former speaker of the U.S. House of Representatives, was riding high just 10 days ago after an upset win in South Carolina's January 21 primary and led in Florida polls as recently as early last week.
But the well-funded and well-organized Romney took back the lead after his two strong debate performances and a blizzard of television advertisements attacking Gingrich.
On the stump on Monday, Romney was breezy and Gingrich combative, reflecting the respective states of their campaigns. Romney cancelled a scheduled Tuesday morning campaign event; Gingrich scheduled four appearances in a final appeal for support on primary day.
Gingrich said Republicans needed to shun Romney and unite behind him if they wanted to defeat Democratic President Barack Obama in November's general election.
If you watch tonight, my prediction is that the conservative vote will be dramatically bigger than Governor Romney's but it will be split, so we've got to find a way to consolidate conservatives and I am clearly the frontrunner among conservatives, Gingrich said on Fox News.
Gingrich has derided Romney as a Massachusetts moderate who raised taxes and fees as governor, enforced a healthcare mandate, and will not provide a sharp enough contrast to Obama.
Romney's attacks have focused on Gingrich's work for troubled mortgage giant Freddie Mac, an ethics probe and his resignation as speaker in early 1999. It has also mocked Gingrich's attempt to ride the coattails of former president Ronald Reagan, a conservative hero.
The campaigns and allied Super PAC fundraising groups had until the end of Tuesday to report whose money they are spending, and how, in an increasingly expensive campaign. Campaign finance filings to the Federal Election Commission will for the first time officially show who contributed money to the Super PACs and fuelled their multimillion-dollar spending sprees.
Reuters/Ipsos poll data on Monday showed Romney's support in Florida at 43 percent versus Gingrich at 28 percent.
When voters hear Gingrich in person they often come away impressed, praising his intellect and toughness.
I was a little undecided between Newt and Mitt but I have decided for sure that Newt's going to get my vote. He's forthright. He says what he means and means what he says, Gene Vandevander of Tampa said at a Gingrich rally.
A straw poll of conservative Tea Party sympathizers in the state released on Monday gave Gingrich 35 percent support against former U.S. Senator Rick Santorum at 31 percent, Romney at 18 percent and Texas congressman Ron Paul at 11 percent.
But other major voting blocs in Florida, including Hispanics, seem to be heavily favouring Romney.
Florida allows early voting at polling stations and by mail, and more than one-third, or 35 percent, of respondents in the Reuters/Ipsos poll said they had already voted. They favoured Romney by a wide margin, the Reuters/Ipsos poll showed.
As Gingrich vows to keep fighting until the nominating convention in August, some voters worried that a nasty, prolonged primary fight would hurt the eventual nominee.
We don't want to attack each other, but to focus on the issues, said voter Jonathan Sanchez of Orlando. We don't want to seem divided.
Florida's 50 delegates are given on a winner-take-all basis. The two other Republicans on the ballot, Santorum and Paul, have moved on to other states.
After Florida's primary, Nevada's February 4 caucuses are the next contest in the process of choosing a Republican nominee.
(Additional Reporting by Steve Holland and Sam Youngman in Florida and Paul Simao in Washington; Writing by Ros Krasny and Patricia Zengerle; Editing by Eric Beech and Paul Simao)