(CNN) -- Republicans have battled fiercely for votes in Tuesday's critical Florida primary, as Democrats have largely ignored the state after national leadership said it would not seat Florida's delegates because of a squabble over scheduling.
Sen. John McCain of Arizona and former Gov. Mitt Romney of Massachusetts appear to be neck-and-neck in the Republican primary. If McCain wins in Florida, his status as the national front-runner will be cemented.
If Romney comes out on top, the battle for the GOP presidential nomination will be up in the air.
The primary calendar is playing in Florida's favor. Other than Republican caucuses in Maine this weekend, Florida is the last contest before the coast to coast primaries and caucuses on February 5, known as Super Tuesday.
"Romney and McCain are competing in Florida's crucial Republican primary as very different candidates, on very different core GOP issues. Romney, on the economy, as the multimillionaire businessman who says he knows how to fix it and says Sen. McCain doesn't get it," said CNN political correspondent Dana Bash.
"McCain is playing the war hero, digging away at Romney's lack of national security experience. McCain calls security and the war on terror the transcendent issue," she added.
McCain, Romney and the three other candidates engaged in a civil debate in Florida Thursday night. But since Friday, the McCain and Romney camps, and the candidates themselves, have fired away at each other over the war in Iraq, the economy, illegal immigration and border security, campaign finance reform and the environment. Watch scenes from the 2008 battle for the White House »
And the negative attacks are not just occurring at campaign events and being reported by the media.
"It's also raging in paid advertising on TV and radio. Romney has spent $30 million on TV ads in Florida this year," said Bash. That's five times as much as the McCain campaign, which is now using less expensive radio commercials to directly question Romney's credibility on the economy.
But McCain and Romney aren't the only candidates with a lot on the line in Florida. Former New York City Mayor Rudy Giuliani has lived in the state over the past month, bypassing the earlier contests to concentrate all his firepower there.
It was a gamble for Giuliani to count on Florida, and he's now an underdog, said CNN political reporter Mary Snow. "Giuliani's been hitting two main themes, national security and his days as mayor of New York during 9/11 and economic security touting his plans for tax cuts," she added.
The two other candidates in the Republican field don't have as much on the line. Former Arkansas Gov. Mike Huckabee has campaigned in Florida, but he's also spent time stumping in some of the southern states that will vote on Super Tuesday.
Rep. Ron Paul of Texas is also concentrating on the February 5 states.
Florida is a closed primary, which means that only registered party members may vote in their own party's primary. McCain won primary contests in New Hampshire and South Carolina, thanks in part to the backing of independent voters who cast ballots in the Republican contests. McCain won't have that luxury in Florida.
"A McCain victory in Florida will be particularly significant because only registered Republicans can vote in the Republican primary. It will be a way for McCain to prove his bona fides with the base," said CNN senior political analyst Bill Schneider. "If Mitt Romney wins Florida, it will be a clear signal that the base is not happy with McCain. The Arizona senator could be facing a conservative revolt."
Nearly 1 million Florida voters have already cast their ballots through early voting and absentees -- a sign the state will likely experience a record turnout despite the fact party sanctions have rendered the Democratic contest meaningless.
According to the Florida Secretary of State's office, more than 474,000 Republicans and just over 400,000 Democrats have already voted. Early voting began January 14 and ended Sunday.
The nearly 1 million Floridians who have voted early already rivals the 1.3 million total voters who participated in the state's 2000 primary -- the last time both party's held a contested primary.
The record-breaking early turnout is likely a result of the highly competitive races on both sides, and Florida's decision to move its primary from mid-March to late January. But that decision drew strict sanctions from both national parties -- the Republicans barred half of Florida's delegates from the convention while the Democrats stripped the state of its delegates entirely.
The nearly 400,00 Democrats who have already cast ballots is particularly surprising, given the leading presidential candidates -- including Hillary Clinton, Barack Obama, and John Edwards -- all pledged not to campaign in the state or run television advertising following the party's sanctions.
But Clinton, who polls show is heavily favored to win the state, has increasingly stressed its importance to the Democratic race. Following her defeat Saturday in South Carolina to Obama, the New York senator said Florida is the next battlefront. Obama has disagreed with her, considering no delegates are at stake.
Clinton has also called on the Democratic Party to formally lift sanctions on the state, and on Sunday, she announced she will be in Florida Tuesday night. E-mail to a friend
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