TAMPA, Fla. - Mitt Romney pushed for a big win over Newt Gingrich Tuesday in Florida's pivotal primary as he seeks to tighten his grip as the front-runner in the race to pick a Republican challenger to President Barack Obama.
Romney enters the day as the heavy favourite in the primary, the final contest in a month of high-stakes elections in which the former Massachusetts governor claimed one win and two second places so far.
Polls show Romney with a double-digit lead in Florida, the fourth and largest state so far to hold a nominating contest. The winner takes all 50 delegates at stake — the biggest prize to date in the state-by-state nominating contests leading to the Republican National Convention in late August in Tampa that will select the nominee.
Romney has been the front-runner for much of the race, but suffered a stunning loss to Gingrich in the Jan. 21 South Carolina primary. But in the span of a volatile week, the race has been turned upside-down.
Romney and his allies have pummeled Gingrich, the former speaker of the House of Representatives, on TV and on the campaign trail. Romney turned in two strong debate performances, while Gingrich faltered. Now opinion polls show Romney with a comfortable lead here.
A Romney win Tuesday is unlikely to end Gingrich's candidacy in a Republican contest that has turned increasingly hostile. . But Romney would have the clear momentum as the race enters a relatively quiet period next month with lower-profile contests, some in states friendly to the more moderate Romney.
Romney has the advantage of more campaign money, a stronger national organization and the support of much of the Republican establishment. Gingrich's populist, sharp-tongued attacks on Obama and media "elites" have helped him emerge as Romney's chief rival, but Romney supports have tried to cast him as too erratic to be an effective nominee or president.
Romney is generally considered the Republicans' strongest candidate to face Obama, whose re-election prospects have been hurt by the slow U.S. economic recovery.
But Romney has had difficulty winning over many Republicans who question his conservative credentials given his shifting views on abortion, gay rights and gun control, as well as the similarities between a Massachusetts health insurance plan he backed as governor and Obama's national plan, which is widely despised by Republicans.
The polls open at 7 a.m. (1200 GMT) across Florida, where Romney offered an increasingly optimistic tone while campaigning in recent days.
"With a turnout like this, I'm beginning to feel we might win tomorrow," an upbeat Romney told a crowd of several hundred at a stop in Dunedin on Monday as he and Gingrich campaigned across the state making their final appeals.
Romney renewed attacks on his rival as an untrustworthy, Washington influence peddler at the outset of two separate appearances Monday. He claimed that Gingrich's ties to federally backed mortgage giant Freddie Mac, despised by conservatives, have hurt the former speaker in a state wracked by the foreclosure crisis.
Gingrich, in turn, acknowledged that his momentum had been checked but promised to remain in the race through the Republican convention. He characterized Romney as an imposter, and his team started to plot a strategy for upcoming contests.
"He can bury me for a very short amount of time with four or five or six times as much money," Gingrich said in a television interview. "In the long run, the Republican Party is not going to nominate ... a liberal Republican."
Romney's campaign cancelled a Tuesday morning rally, but scheduled a night celebration at the Tampa Convention Center. Gingrich planned a blitz of local television interviews and appearances at polling places in Orlando, Lakeland and Celebration — — before gathering with supporters for a primary night party in Orlando. The last polls close at 8 p.m. EST (0100 GMT).
The other two candidates in the race will not be in Florida on Tuesday. Both former Pennsylvania Sen. Rick Santorum and Texas congressman Ron Paul have ceded Florida's primary to Romney and Gingrich in favour of smaller, less-expensive contests. They will spend the day campaigning across Colorado and Nevada.
Romney and his allies have poured more than $14 million into Florida television advertising primarily to attack Gingrich, who has struggled to compete with Romney's fundraising ability, staffing and network of high-profile supporters. Gingrich and his allies spent roughly $3 million on Florida advertising.
"We are pitting people power versus money power," Gingrich said Monday as he tried to rally his shrinking base of support.
Republican officials in Florida were anticipating a big turnout, more than 2 million voters, up from a record 1.9 million in the Republican primary in 2008. More than 605,000 Floridians had already voted as of Monday, either by visiting early voting stations or by mailing in absentee ballots, ahead of the total combined early vote in the Republican primary four years ago.
Romney easily won the New Hampshire primary after nearly winning the leadoff Iowa caucuses which Santorum won by several dozen votes. The South Carolina setback behind him, Romney sought to aggressively stop Gingrich, aided by a well-funded political action committee that supports him and is run by former political aides.
Associated Press writers Thomas Beaumont, Kasie Hunt, Shannon McCaffrey and Brendan Farrington contributed to this report.