NORTH CHARLESTON, S.C. (AP) - Front-runner Mitt Romney and his presidential pursuers enter the final full day of campaigning in a South Carolina GOP primary contest significantly altered from just 24 hours earlier.
The former Massachusetts governor is looking to fend off challenges to his fragile lead from more conservative rivals Newt Gingrich and Rick Santorum.
The entire field, including Ron Paul, scrambled for the shreds of support left by Texas Gov. Rick Perry who quit the race Thursday.
Perry's departure, a raucous Charleston debate and fresh reminders of Gingrich's tumultuous personal life promised to make the dash to Saturday's voting frenetic and the intra-party attacks increasingly sharp.
"I've been fighting for health reform, private sector, bottom-up ... for 20 years, while these two guys were playing footsies with the left," Santorum said of Romney and Gingrich during a heated debate exchange.
With Romney clinging to a narrow lead in South Carolina polls and Gingrich closing in, Santorum was aiming for the top tier. Paul was also a factor as the four remaining GOP hopefuls planned to scatter across the Palmetto State on Friday.
Romney, whose lead has shrunk in the race's closing days, planned stops along the coast, in the state's midlands and conservative north. Gingrich, gaining fast and buoyed by Perry's endorsement, was planning a half-dozen stops concentrating in the south, especially the heavily pro-military Charleston area.
Meanwhile, Santorum, the former Pennsylvania senator seeking to consolidate conservatives, planned to rally supporters in four stops statewide, including the conservative upstate, the home of his evangelical base.
The libertarian-leaning Paul, whose support has slipped with his light campaign effort here, hoped to whip up his supporters with a six-city fly-around.
The GOP race spun wildly Thursday, beginning with news that Santorum had edged Romney in Iowa, a reversal of the first nominating contest more than two weeks past.
Perry, having struggled in vain to build support in his native South, quit and endorsed Gingrich. Gingrich, meanwhile, faced stunning new allegations from an ex-wife that he had sought an open marriage before their divorce. An aggressive debate punctuated the day.
Santorum played aggressor during the faceoff, trying to inject himself into what seemed increasingly like a Romney-Gingrich race after Perry's endorsement of his onetime rival.
"Newt's not perfect, but who among us is," Perry said in backing Gingrich. "The fact is, there is forgiveness for those who seek God and I believe in the power of redemption, for it is a central tenet of my own Christian faith."
Gingrich angrily denounced the news media for putting his ex-wife front and center in the final days of the race and spreading her accusations. "Let me be clear, the story is false," he said when asked at the opening of the debate about her interview.
Santorum, Romney and Paul steered clear of the controversy.
"Let's get onto the real issues, that's all I've got to say," said Romney, although he pointed out that he and his wife, Ann, have been married for 42 years.
Gingrich and Santorum challenged Romney over his opposition to abortion, a well-documented shift but a potent one in evangelical-heavy South Carolina.
Recent polls, coupled with Perry's endorsement, suggested Gingrich was the candidate with the momentum and Romney the one struggling to validate his standing as front-runner.
Gingrich released his income tax records during the course of the debate, paving the way to discussing Romney's. The wealthy former venture capitalist has said he will release them in April, prompting Gingrich to suggest that would be too late for voters to decide if they presented evidence Obama could exploit.
"If there's anything that's in there that's going to help us lose the election, we should know before the election. If there's not, why not release it?" Gingrich said. His effective tax rate, roughly 31.6 percent of his adjusted income, was about double what Romney told reporters earlier this week he had paid.
Gingrich grappled with problems of a different, possibly even more crippling sort in a state where more than half the Republican electorate is evangelical.
Marianne Gingrich told ABC's "Nightline" that her ex-husband had wanted an "open marriage" so he could have both a wife and a mistress. She said Gingrich conducted an affair with Callista Bistek, now his wife, "in my bedroom in our apartment in Washington" while she was elsewhere.
"He was asking to have an open marriage and I refused. That is not a marriage," she said in excerpts released by the network well ahead of the debate.