Gingrich will win South Carolina primary, CNN projects

• NEW: Romney: "This race is getting to be even more interesting"
• CNN projects Gingrich will win South Carolina primary
• Gingrich surged in polls in week leading up to primary
• Romney comes off a tough week with Santorum's official Iowa win

Columbia, South Carolina (CNN) -- CNN projects that Newt Gingrich will win Saturday's South Carolina GOP presidential primary, a development that would mark a stunning turnaround for a campaign that observers had left for dead -- again -- just weeks ago.

According to exit polls, Gingrich had 38%, with former Massachusetts Gov. Mitt Romney getting 29% and former U.S. Sen. Rick Santorum getting 17%. U.S. Rep. Ron Paul of Texas had 15%, according to the exit polls.

"Thank you South Carolina!" Gingrich's campaign posted to Twitter after polls closed at 7 p.m. ET, adding a link to his campaign donation website. "Help me deliver the knockout punch in Florida."

This would be the first time since 1980 that three different GOP candidates won nominating contests in Iowa, New Hampshire and South Carolina.

Less than a week ago, Romney, the New Hampshire winner, was looking at a double-digit lead in most polls of likely voters in South Carolina's primary, a big lead in Florida and the possibility of a clear path to the GOP nomination. But Gingrich turned in two strong debate performances in the state this week while Romney was put on his heels by his rivals.

Romney congratulated Gingrich in remarks to his supporters after polls closed Saturday night. CNN projected Romney would finish second in South Carolina

"This race is getting to be even more interesting," Romney said. "... We're now three contests into a long primary season. This is a hard fight because there is so much worth fighting for."

"We've still got a long way to go and a lot of work to do, and tomorrow we're going to move on to Florida," Romney added, referring to the next contest, scheduled for January 31. "It's a state that has suffered terribly under the failed policies of President Obama."

Gingrich's turnaround, after he finished fourth in Iowa and New Hampshire, is just his latest. He came out of nowhere to top national polls in late fall on the strength of debate performances, but dropped again ahead of the Iowa caucuses as opponents hammered him in Iowa ads.

"Gingrich has been harder to kill than Rasputin," Republican strategist and CNN contributor Alex Castellanos said Saturday. "He has been dead three times in this campaign, and ... the guy keeps coming back."

Gingrich had been building up momentum all week. A poll released Saturday morning showed the former House speaker's surge over the last week carrying him past Romney, who had been the front-runner in the state all month. The American Research Group poll shows Gingrich leading Romney by a 40% to 26% margin. ARG's last poll, released Thursday, showed a virtual tie with Gingrich at 33% and Romney at 32%.

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A day before the South Carolina vote, Romney's camp was downplaying expectations and Gingrich's predicting victory.

"It's tight, it's real tight," said one Romney adviser who did not want to be quoted discussing internal poll numbers.

A top Gingrich strategist in South Carolina was predicting victory.

Richard Quinn, a longtime South Carolina GOP strategist who worked for Jon Huntsman but signed on to advise Gingrich this week, told CNN Friday that the former House speaker will walk away with "between a 4- and 6-point plurality win" in the contest.

South Carolina is the third contest on the primary calendar and the first in the South. The winner of the primary has gone on to win the Republican nomination in every election since 1980.

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Gingrich and Romney were both campaigning in the conservative Upstate on Saturday with Gingrich presenting himself as the conservative alternative to the "Massachusetts moderate" Romney while Romney continued to attack Gingrich as he has over the past week as polls tightened.

At his Greenville campaign headquarters, Romney launched a new line of attack, calling for Gingrich to release details on his work for government-backed mortgage giant Freddie Mac, an institution unpopular with conservatives.

"Didn't he say he was going to release information about his relationship there?" Romney asked. "Let's see what report he wrote for Fannie Mae and Freddie Mac, what his conclusions were and what the contract looked like. I thought he said he was going to do that."

Later making calls at a phone bank inside the headquarters, Romney gave an idea of how he sees the race on one of the five calls he made: "This could be real close," he said.

Romney's campaign also has been pressing the former House speaker to release the full report from a 1990s ethics investigation that led to his downfall in Congress. Gingrich was reprimanded by the House and ordered to pay a $300,000 penalty in 1997 for violating an ethics rule.

This week, Romney's campaign sent Gingrich a cake marking the 15th anniversary of that reprimand, according to a Romney campaign source. A picture provided by that source shows the wording "Happy 15th anniversary, Mr. Speaker! ... Now release the records," written in icing on the cake.

An anticipated run-in between the two front-runners didn't materialize at a Greenville restaurant where both had booked events at the same time. Romney showed up about 45 minutes early and had left before Gingrich arrived.

Upon arriving, Gingrich asked, "Where's Mitt? I thought he was going to stay and maybe we'd have a little debate this morning."

Strong thunderstorms were rolling through the state on Saturday and the state election commission said turnout across the state ranged from very light in some areas to very heavy in others.

As late as Tuesday, Romney had a double-digit lead in most polls of likely voters in the state's primary. Then what had been declared an eight-vote Romney victory in Iowa's January 3 caucuses was reversed into a 34-vote win for Rick Santorum when the state party certified its results on Thursday.

Later that day, Texas Gov. Rick Perry suspended his campaign and threw his support to Gingrich.

"It has been a hard week," state treasurer Curtis Loftis, a leading Romney surrogate, said Friday. "Nobody is going to deny that."

Santorum trailed Romney and Gingrich in pre-primary polls, and the Iowa reversal and an earlier endorsement by a group of leading conservative Christian leaders hasn't translated into support in a state where a large part of Republican voters call themselves evangelical or conservative Christians.

But the former Pennsylvania senator said on Friday that he had felt a "palpable change" over the last 48 hours.

Santorum has spent the week trying to bring down Gingrich in what most see as a race between the moderate Romney against conservatives Gingrich or Santorum.

On Friday, he made parallels to Goldilocks and the Three Bears, calling Gingrich's history too hot, questioning whether he had the "discipline to go out and be steady," and Romney as "just a little cool, just a little timid."

Left out of Santorum's fable is Texas Rep. Ron Paul, although most polls show him running just a few points behind Santorum.

Although most GOP strategists see Paul's strict interpretation of the Constitution and his views on defense and spending as out of step with the mainstream, he appeals to libertarian-leaning Republicans and has a large following among younger voters.

On Friday, Paul addressed that appeal, saying, "A lot of people do identify me with another generation, the younger generation who's so enthusiastic about the things that we've been talking about in going back to the Constitution," Paul said. "So this to me is very encouraging because the growth of the freedom movement is getting to be exponential. It was very, very slow for a long time."

The ARG poll showed Paul running five points ahead of Santorum, 18% to 13%

The campaign trail leads to Florida next, which votes on January 31. Romney has held a large lead in polls of likely primary voters but recent polls show the race tightening a bit there, too.

CNN's Jim Acosta, Adam Aigner-Treworgy, Dana Bash, Peter Hamby, John Helton, Jason Hanna, Shawna Shepherd and Paul Steinhauser contributed to this report.