Although Nevada holds caucuses Saturday as well, the spotlight is on the first-in-the-South primary; no Republican since 1980 has won the party nod without a South Carolina triumph.
"Truly anything can happen," Katon Dawson, the state party chairman, said Wednesday, hours after Mitt Romney won his native Midwestern state. "Michigan just shuffled the deck. It's a whole new game in South Carolina, and, with the undecideds, it can go any way."
The latest South Carolina polls show a close race. A flood of negative phone calls, hard-hitting mail and late-deciders could change that overnight.
Not even two weeks into voting, three candidates each have one major win thanks to three different constituencies, a reflection of a deeply divided GOP and the absence of an obvious successor to President Bush.
Mike Huckabee, the former Arkansas governor and ordained Baptist minister, prevailed in the Iowa caucuses with the support of fellow evangelicals. John McCain, the four-term Arizona senator, repeated his 2000 victory in New Hampshire with the overwhelming support of independents. And Romney, the former Massachusetts governor, rallied Republican loyalists to post his first major win in Michigan; he also won barely contested Wyoming.
On Wednesday, the three set their sights on South Carolina, where rival Fred Thompson, the actor and former Tennessee senator, has been camping out with hopes of a surprise upset that would upend the race yet again.
Such an extraordinarily fractured field plays right into the strategy of former New York Mayor Rudy Giuliani, last year's national front-runner who is on the brink of irrelevancy after badly losing the first four contests.
Giuliani has planted himself - and his dwindling campaign account - in Florida in hopes of winning its primary Jan. 29, grabbing its winner-take-all 57 delegates and emerging as the GOP leader heading into Feb. 5 when some two dozen states vote.
South Carolina and Nevada are next up - and the race dynamics could shift thereafter.
"A different person will win Saturday in South Carolina," Thompson declared in Laurens, S.C., an obvious reference to himself given that he hasn't prevailed to date.
The Tennessean figures he has a home-field advantage in the Southern state. He needs a win to keep his fragile and cash-strapped candidacy alive. Anything less than first place would probably force him to drop out.
After a third-place win in Iowa, Thompson skipped New Hampshire and Michigan for a bus tour through South Carolina. He styled himself as the most consistent conservative and a states-rights candidate. He is trying to take votes from Huckabee's far-right support by portraying his rival as liberal on everything from economic issues to foreign policy. More contrasts are certain in the final days.
Huckabee hopes to rally religious conservatives in the Bible Belt as he did in the Heartland with a pitch that's heavy on faith and helping the working man. His base is in the ultraconservative Upstate around Greenville and Spartanburg. Still, he's not taking that region for granted; he will campaign by plane and bus across the state.
Huckabee's aides view South Carolina as a race between their boss and McCain but also are awaiting any impact Romney may have following his win in Michigan. Huckabee also is bracing for criticism from Washington-based interest groups, such as the anti-tax group, the Club for Growth, which is seeking to derail him. The former Southern governor argues that he's an outsider who can clean up Washington.
Romney threatens to take conservative votes from Thompson and Huckabee if he gets any bounce out of Michigan.
Next to McCain, he has one of the strongest organizations in South Carolina, and has laid the ground work to capitalize on a victory. He has spent more than $3 million on TV ads and direct mail. After spending months struggling to find a clear message, he's sticking with one that worked in Michigan - an economic appeal amid job losses combined with a fix-Washington pitch to voters seeking change.
He's splitting the next four days between South Carolina and Nevada.
Romney is the only top Republican contender to pay serious attention to the Western state's caucuses; 31 delegates are at stake compared with 24 in South Carolina. Nevada ranks in the top five of states with the most Mormons and, as a member of that faith, Romney could benefit. Turnout is expected to be low - roughly 25,000 - and that could pave the way for a strong finish, perhaps even first place, by libertarian Ron Paul. The Texas congressman has been on TV and radio in the state for a long stretch.
"I'm not looking for gold stars on my forehead like I was in first grade. I want delegates," Romney said in Bluffton, S.C. He lowered expectations for himself in South Carolina, while raising them for McCain, saying the senator had the primary "pretty well wrapped up."
McCain hopes that's the case. He is banking on his three rivals splitting the right-flank vote and giving him an avenue to win among moderate Republicans whose numbers have swelled in the state in the eight years since he lost to George W. Bush. This time, it's McCain who has locked up the endorsements of much of the state's GOP establishment.
A former Vietnam prisoner of war with decades of experience on military issues, McCain is emphasizing his background as he argues that he's the most qualified to be commander in chief. The pitch could play well in a state with large numbers of active duty military and veterans. McCain also is arguing that he's the most likely to win against a Democrat in the fall, and will put his economic pitch up against Romney's, claiming that the ex-governor's record on the economy is nothing to brag about.
"We need your vote, and if we can get it, we're going to win in South Carolina," a cautious-though-optimistic McCain said in Greenville, S.C.
