With more lead changes than an impossible-to-predict contest down at the racetrack, Tuesday's (January 29) Republican primary in Florida has the potential to be a coronation and widow-maker for a trio of GOP presidential hopefuls. For former New York Mayor Rudy Giuliani, the Sunshine State is his Waterloo, a last-ditch chance to get into a race he has mostly experienced from the sidelines as of late.

For front-runners Senator John McCain and former Massachusetts Governor Mitt Romney, Tuesday's contest is the most delegate-rich one to date — 57 are at stake — and a potential launching point to build strong momentum heading into February 5's pivotal "Super Tuesday" showdown, where 23 states will hold primaries or caucuses that could finally put into sharper focus who the GOP candidate will be.

As for the Democrats, well, like Michigan, Florida's delegates are taking a forced break due to the state's decision to move its primary up before the 5th. For now, no Democratic delegates are at stake, but that could change if the race continues to be as tight as it is and those delegates are needed to break a deadlock.

Here's a preview of what's at stake on Tuesday for the major candidates still in the race.

Rudy Giuliani

Best-case scenario: Giuliani has bet the house on Florida and with good reason: New Yorkers (or ex-New Yorkers) account for almost 15 percent of the state's population. A good showing could finally help his campaign catch fire and set him up for a bounce going into next week.

Worst-case scenario: For the most part, the above is pretty pie-in-the-sky. Giuliani's failure to make even a small dent in the early contests is bad enough, but his double-digit lead in Florida has completely evaporated over the past few weeks, despite his months of constant politicking in the state, and he is now expected to finish a distant third at around 14 percent, to the extent that the polls can be trusted. The upside is it would be his best showing to date, but the downside is it would almost certainly spell the end of a campaign that might put a permanent tarnish on the formerly (semi-) glossy image of "America's Mayor."

John McCain

Best-case scenario: In a state where 40 percent of Republicans claim to have "ties" to the military, according to The New York Times, Vietnam veteran and Iraq "surge" supporter McCain is in his sweet spot: National security and Iraq are among the most important topics on voters' minds there. He's been campaigning heavily in the state, and the momentum from his recent South Carolina triumph combined with a Florida win might finally put some space between him and Romney. Though most polls at press time had him in a dead heat with Romney, some had him with a three-point advantage, which, while slight, would still give him all 57 delegates if he were able to hold onto it in the winner-takes-all contest.

Worst-case scenario: Because the primary is only open to registered Republicans, McCain can't count on the Independents and crossover Democrats who helped him win in New Hampshire. And, though the punishment wasn't as harsh as the one that was doled out by the Democratic Party, the Republican Party halved the amount of delegates up for grabs in Florida to 57, which means an uncontested victory could have put McCain in the driver's seat. Also, Romney has been blasting McCain for his alleged lack of economic bona fides, which could sway some of the retirement-age voters who are living on fixed incomes and worried about the economy.

Mitt Romney

Best-case scenario: With a vast war chest, former CEO Romney has been able to spend lavishly on TV advertising in the expensive Florida media market, and given that the state has a population of more than 18 million, the TV route is the best way to reach voters. He has continued to use his extensive business background as a selling point in a state that has been hit hard by the tanking real-estate market.

Worst-case scenario: Even a slim loss is a total loss in Florida, given that it's a winner-takes-all contest. If Romney, who has reportedly not yet decided in which states he wants to focus his attention in the "Super Tuesday" race, loses Florida and makes even just a few miscalculations over the next week, his once-promising bid to be the first Mormon to win a presidential nomination could be in serious trouble.

Mike Huckabee

Best-case scenario: The former Arkansas governor regains some momentum after a string of second- and third-place finishes by appealing to the state's evangelicals, who comprise a quarter of Florida's Republican voters.

Worst-case scenario: Huckabee suffers another loss in a key Southern state and his funding dries up, possibly forcing him to pack it in.

The Democrats

Best-case scenario: The race is so close in the stretch that if the 210 Democratic Florida delegates are brought back into play down the line, they could help finally cement a front-runner. If pre-election polls are to be believed, Senator Hillary Clinton snags the prize with a predicted 20-point win over rival Senator Barack Obama, and the subsequent media coverage. Also, since registered Democrats will be able to vote anyway, the importance of the Florida vote could convince the national party that it should rethink its reliance on making the Iowa and New Hampshire races so sacrosanct. The primary process could get a serious shake-up to allow larger, more diversity-heavy states a chance to weigh in earlier.

Worst-case scenario: After not campaigning here to honor the national party's punishment of the state for holding a January primary against party rules, Clinton's decision to fly to Florida on election eve to celebrate her expected "victory" could highlight the increasingly desperate feeling of her campaign. Tens of thousands of Florida voters feel disenfranchised and disillusioned, heaping yet another dose of bad election mojo on the state that put "hanging chads" into the national lexicon.

Are you obsessing over the 2008 presidential election as much as we are? Don't miss our Tuesday night coverage of the Florida primary, and be sure not to miss MTV/MySpace's "Closing Arguments: A Presidential Super Dialogue" on Saturday. Senator Hillary Clinton and Mike Huckabee are already onboard for the live interactive forum, which will be broadcast from the MTV studios in New York. The event will air on MTV, MTV2 and MTV Tr3s, with highlights on mtvU; stream online at ChooseOrLose.com and MySpace.com, as well as on mobile devices via MTV Mobile; and be broadcast live on MTV Radio.