WARRENVILLE, S.C. -- Newt Gingrich was surging in South Carolina hours before the state’s crucial Republican primary Saturday, but in typical Gingrich roller-coaster fashion, a late-breaking scandal threatened to derail his campaign just as it was peaking.

A series of South Carolina polls released Thursday showed Gingrich closing the gap with front-runner Mitt Romney, and several showed the former speaker of the House of Representatives edging into the lead. In addition, Rick Perry endorsed his one-time rival as the Texas governor dropped out of the race.

Gingrich’s commanding performance in Monday night’s debate galvanized his campaign. All week he’s been drawing the loudest, most eager crowds. He appeared to be peaking just as Thursday night’s final pre-primary debate gave him an opportunity to break through to a stunning victory Saturday, possibly upsetting the dynamic of the Republican presidential campaign.

Except that at that very moment an unexpected thundercloud burst over the Gingrich campaign: ABC News released excerpts from Thursday night’s Nightline featuring his second wife, Marianne, saying that her husband had wanted her to stay married to him while he had an affair with a young House aide, Callista Bisek, whom he’s since married.

Gingrich, she said, asked whether she would “share” him with Bisek.

“And I just stared at him and he said, ‘Callista doesn’t care what I do,’ ” Marianne Gingrich told ABC. “He wanted an open marriage and I refused.”

She said her husband “always called me at night and always ended with ‘I love you.’ Well, she was listening.”

All this was occurring while Gingrich was leading the impeachment of President Bill Clinton on charges of lying in court proceedings about his own extramarital dalliances.

It’s not clear what impact these revelations may have on the primary, but 60 percent of South Carolina GOP voters in the 2008 primary identified themselves as evangelical Christians, and they may find this hard to forgive.

Still, polls showed Gingrich surging in the state. An NBC-Marist poll showed Romney leading Gingrich by 15 points Monday, but after that night’s debate, Romney’s lead shrank to 5 points by Tuesday night. On Thursday a more recent Rasmussen Reports poll had Gingrich ahead by 2 points; an InsiderAdvantage survey put him up by 3 points; and a Public Policy Polling survey had him ahead by 6.

Gingrich’s career has been filled with dramatic ups and downs. Many voters can’t get past his record as a polarizing figure who made millions as a Washington insider and had to pay a $300,000 penalty for ethical lapses while he was speaker. Many voters here already were troubled by his personal life.

“I like Newt, but I’m really struggling with my vote. I’m scared he has too much baggage,” said Craig LaCross of Florence.