WASHINGTON -- Former House Speaker Newt Gingrich came from behind to win the Republican presidential nomination contest in South Carolina Saturday, defeating former Massachusetts Governor Mitt Romney, the front-runner,  by double digits, results showed.

With 99 percent of precincts reporting, television reports said Gingrich took 40 percent of the votes in the primary in South of the country, with Romney a distant second at 28 percent.

Former Senator Rick Santorum of Pennsylvania was third with 17 percent and Congressman Ron Paul of Texas fourth with 13 percent. Both pledged to remain in the race.

CNN exit polling indicated South Carolina voters see Gingrich as more electable than Romney, based on his debate performances.

It was a striking development in a months-long Republican nominating contest that has seen the restive base of conservative voters ping-pong among the alternatives to the party establishment’s favorite, Romney.

With late-night tallies showing Gingrich beating Romney by 12 percentage points, it was no small win. Exit polls showed Gingrich had done it with a formidable coalition of groups that have resisted Romney’s candidacy all election season long: evangelical Christians, Tea Party movement supporters and those who call themselves “very conservative.”

Gingrich now heads to Florida, where he faces a daunting test in seeking to capitalize on his new status as the candidate who poses a singular, insurgent threat to Romney. He used his victory speech to cast himself as the champion of the party’s anti-establishment wing, reprising his popular castigation of the news media and other “elites” while keeping his focus on the defeat of President Barack Obama in the November elections.

Standing beside his wife, Callista, as he addressed an exuberant crowd in Columbia, Gingrich attributed his victory to “something very fundamental that I wish the powers that be in the news media will take seriously: The American people feel that they have elites who have been trying for a half-century to force us to quit being American."

"People completely misunderstand what's going on. It's not that I'm a good debater. It's that I articulate the deepest-felt values of the American people," Gingrich said.

Gingrich praised Santorum, Paul and even Romney, calling him a "good example of America," touting Romney's success in business and in organizing the 2002 Salt Lake City Winter Olympics. He then turned his sights on President Obama, the Democrat he hopes to face.

"This is the most important election of our lifetime. If Barack Obama can get re-elected after this disaster, just think how radical he would be in a second term. …

"The centerpiece of this campaign, I believe, is American exceptionalism versus the radicalism of Saul Alinsky," the founder of modern community organizing, Gingrich said.

Obama, who touted his work as a community organizer during the 2008 campaign, gets his support from "people who don't like the classical America," Gingrich said, calling Obama the "most effective food-stamp president in history."

"We don't have the kind of money that at least one of the candidates has, but we do have ideas, and we do have people. And we proved here in South Carolina that people power with the right ideas beats big money, and with your help, we're going to prove it again in Florida," Gingrich concluded.

Romney earlier acknowledged Gingrich's victory Saturday but also took aim at the new front-runner, comparing him to President Obama.

"President Obama has no experience running a business and no experience running a state. Our party can't be led to victory by someone who also has never run a business and never run a state," Romney said.

"Our president has divided the nation, engaged in class warfare and attacked the free-enterprise system that has made America the economic envy of the world. We cannot defeat the president with a candidate who has joined that very assault on free enterprise," he said, adding, "Those who pick up the weapons of the left today will them turned against us tomorrow."

Pelting rain kept voting lines short throughout the day, possibly cutting turnout, observers said.

Romney's fortunes had faded in the Palmetto State in recent days, with news his initial razor-thin win in the Iowa caucuses is now considered a tie with Santorum and Gingrich making headway in South Carolina by painting Romney as a "Massachusetts moderate."

Gingrich's strong performance in Thursday's debate in Charleston, which included a strong defense against accusations by an ex-wife, helped boost his numbers.

Former Alaska Governor Sarah Palin, the 2008 GOP vice presidential nominee, called on South Carolina voters to choose Gingrich as the conservative alternative to Romney and keep the primary contest alive.

Romney won the New Hampshire primary earlier this month, and Gingrich's win Saturday marks three different results in the first three contests.

The campaign moves to Florida next, where voters have been casting early ballots in advance of the Jan. 31 primary.