Former House Speaker Newt Gingrich, former Massachusetts Gov. Mitt Romney, and former Pennsylvania Sen. Rick Santorum were in the state Thursday on separate visits. Ex-Arkansas Gov. Mike Huckabee is set to be at a get-out-the-vote rally in Columbia on Saturday evening.
South Carolina, which holds the nation's first-in-the-South presidential primary, is among several early-voting states where Republicans with possible ambitions to challenge President Barack Obama are courting donors and stirring interest.
Gingrich was set to hold a "jobs here, jobs now" rally in Greenville, a conservative stronghold in the red state. His political action committee gave $3,500 last month to Republican gubernatorial candidate Nikki Haley.
Santorum had three events in Greenville earlier in the day and helped set up a fundraiser for Haley in Philadelphia in September.
But Haley, a three-term House member running as a political outsider, is appearing only with Romney. They campaigned together in Summerville and in her rural hometown of Bamberg, before she continued on several stops in Beaufort County as part of her statewide bus tour.
Romney's PAC has contributed more than $60,000 to Haley's gubernatorial bid, according to campaign filings.
Romney endorsed her in April as she badly trailed her three primary rivals. Former Alaska Gov. Sarah Palin endorsed her a month later, helping to catapult her bid. Palin's PAC gave $3,500 to Haley earlier this month.
Haley spokesman Rob Godfrey said Romney and his wife have been tremendous assets to Haley's campaign, endorsing her at a time when people asked, "Nikki who?"
Haley's Democratic opponent, Sen. Vincent Sheheen, had events Thursday in Horry County, Florence and Orangeburg. His spokesman, Trav Robertson, says it's not surprising to see national GOP political figures in the state before the election. He argues it shows Haley is in trouble and needs the support.
But political scientist Scott Huffmon said it has more to do with presidential politics and South Carolina's importance in the selection process.
"We're the first test of the real conservative wing of the Republican Party," said Huffmon, a Winthrop University professor and poll director. "They need to do well in South Carolina."
The state election gives possible presidential hopefuls an opportunity to address Republican voters as they're paying attention, to boost their image and name recognition, he said.
Since 1980, the winner of South Carolina's primary has won the GOP nomination.
Only Iowa, New Hampshire, South Carolina and Nevada can hold their contests in February 2012. States that divide up delegates proportionally will vote in March and winner-take-all states will go in April, according to the Republican National Committee's plan approved in August.