After a fiery debate Thursday night that saw the former House speaker spar with top rival Mitt Romney, Gingrich on Friday aimed to capitalize on what polls show is increased momentum for his campaign one day before the vote here.
With the primary shaping up as a nail-biter, the four remaining candidates made a last gasp effort Friday to win southern conservatives as they chase their party's nomination to go up against President Barack Obama in November elections.
Gingrich was scheduled to visit a children's hospital, while Romney, whose aura of inevitability has eroded in recent days, issued an open letter to South Carolina voters insisting he was "not a career politician" but a successful businessman who can turn the US economy around.
The question remained whether he could turn his fortunes around in the Palmetto state in the coming 24 hours.
A Public Policy Polling (PPP) survey released Thursday showed Gingrich with a six-point lead over Romney, 35 to 29 percent, with Texas Representative Ron Paul and former Pennsylvania senator Rick Santorum tied at 15 percent.
Respected Washington website Real Clear Politics' average of recent polling data showed Gingrich with a one percentage point lead over Romney in the state.
Gingrich has risen with a series of feisty debate performances, and on Thursday drew a standing ovation from the crowd with a blistering reply to the first question, on marital infidelity.
Asked about his second ex-wife's claim in a TV interview that he asked her to have an "open marriage," Gingrich denied the claim as "false" and called the question "as close to despicable as anything I can imagine."
"I am tired of the elite media protecting Barack Obama by attacking Republicans," thundered Gingrich, who as speaker in the 1990s hounded Democratic president Bill Clinton over an extra-marital affair.
Gingrich had his own six-year affair with an aide who is now his third wife. He has since converted to Catholicism and expressed regret over past failings.
He aimed for a surprise victory here over Romney after warning that a win in South Carolina by the former Massachusetts governor and multi-millionaire investor would hand the party's nomination to a moderate.
Romney strove to deflect attacks from Gingrich that he built his vast fortune while firing workers, saying he expected such jibes from Obama, not fellow Republicans -- traditionally the party of business.
"I know we're going to get hit hard from President Obama, but we're going to stuff it down his throat and point out (that) it is capitalism and freedom that makes America strong," Romney said.
Gingrich charged that the approach of Romney's Bain Capital firm was to "take over a company and dramatically leverage it, leave it with a great deal of debt, (make) it less likely to survive."
Santorum, a Christian conservative, joined in, saying Republicans must help "working men and women of this country who are out there paddling alone."
Romney struggled with a question about when he would make public his tax filings -- as is customary for presidential contenders -- days after he revealed he paid just 15 percent of his income to the government.
"I'll release my returns in April and probably for other years as well," he said, describing himself as "someone who's lived in the real streets of America."
As in the debate, Romney in his open letter Friday trained his fire on the Democratic incumbent he hopes to take on in November.
"If we are going to undo the damage, this year's election is critical," he wrote.
"We can choose to live in the entitlement society that Barack Obama has been constructing, a society built around dependence on government. Or we can return to the merit-based opportunity society built by our founding fathers."
Romney, the party establishment's favorite and the off-again, on-again frontrunner over the past year, pulled in then endorsement of Virginia Governor Bob McDonnell, who on Friday described Romney as "the best chance to be able to defeat president Obama in November."
Romney has hoped a convincing win here would let him wrap up the nomination, but he faced several setbacks on Thursday: Texas Governor Rick Perry dropped out of the race and endorsed Gingrich, and Iowa authorities rescinded Romney's eight-vote victory in the heartland state's first-in-the-nation caucus and declared Santorum the winner.