CHARLESTON, S.C -- . Newt Gingrich won the South Carolina Republican primary Saturday, a stunning come-from-behind upset that shook the contest for the party’s presidential nomination like an earthquake.

Gingrich was declared the winner virtually as soon as the polls closed at 7 p.m. Mitt Romney was declared the runner-up.

Gingrich, 68, the former congressman from Georgia and speaker of the House of Representatives from 1995 to 1999, surged in the last five days to score the dramatic victory. His commanding performances in two debates this week turned the tide in South Carolina.

Mitt Romney, 64, finished a disappointing second, after watching his double-digit lead in state polls evaporate amid charges that he’s a wealthy corporate raider with something to hide in offshore bank accounts and personal tax records that he’s declined to disclose.

Ron Paul, 76, and Rick Santorum, 53, vied for third and fourth, as early returns were inconclusive.

The results signaled a party unwilling or unable at this early stage to rally to any one candidate as their champion to challenge Democratic President Barack Obama in the fall. With a recount in Iowa changing the initial result, the party now has produced three winners in as many states: Rick Santorum in Iowa, Romney in New Hampshire, and now Gingrich in South Carolina.

The head-snapping turn of events over five days saw Romney end the week having lost two out of the first three contests. As late as Tuesday, he thought he had won Iowa, knew he’d won New Hampshire, and led by a comfortable margin in South Carolina, where every winner since 1980 has gone on to win the Republican nomination.

At stake Saturday were 25 delegates, with 1,144 needed to clinch the nomination at the Republican National Convention in Tampa, Fla., the final week of August. The winner of the South Carolina vote will get 11 delegates; the popular-vote winner in each of seven congressional districts will get 2 delegates.

Next up: a slugfest in Florida, with two high stakes debates before voting — which started Saturday — ends on Jan. 31.

South Carolina voters were divided between the two candidates topping the polls.

Gingrich’s three marriages and admissions of affairs made no shred of difference to many voters, including Rema Thomas, 60, of Chapin, S.C., an evangelical who decided on Gingrich after watching the two S.C. debates.

“No one does not have baggage. Newt’s was just exposed more because of his time in politics,” she said. “I think it’s time for a bulldog president. Grab ‘em by the pants leg and don’t leg to until you draw blood. That’s Newt.”

Thomas said she knows Gingrich is a “hot head,” but with the sorry state of the country and a questionable crowd running the show in Washington, “what do we have to lose?”

Romney signaled Saturday that he’ll escalate attacks on Gingrich heading toward Florida, at the same time that he belatedly agreed to a second debate in the state this week. The candidates will debate Monday night in Tampa and Thursday night in Jacksonville.

(Steve Thomma and David Lightman report for McClatchy’s Washington bureau. Gina Smith reports for The State in Columbia, S.C. Amy Sherman of The Miami Herald contributed to this report from Pompano Beach, Fla.)