(Reuters) - Newt Gingrich jolted the Republican presidential race on Saturday with a convincing come-from-behind victory in South Carolina, where voters rejected frontrunner Mitt Romney's pitch that he is the best bet to fix a broken economy and defeat President Barack Obama.
Gingrich's win injects unexpected volatility into a Republican nominating race that until this week appeared to be a coronation for Romney, the former Massachusetts governor and private-equity chief.
Three different candidates now have won the first three contests in the state-by-state battle for the Republican presidential nomination to face Obama, a Democrat, on November 6.
Former senator Rick Santorum won the Iowa caucuses on January 3 and Romney won the New Hampshire primary on January 10. Gingrich fared poorly in both those states and had trailed badly in South Carolina polls.
Riding a series of feisty debate performances, Gingrich captured the lingering unease of conservative voters in South Carolina who view Romney's moderate past and shifting policy stances with suspicion. The former speaker of the U.S. House of Representatives argued that he would be able to better articulate the party's conservative ideals.
With 65 percent of the vote counted, Gingrich had pulled in 41 percent of the vote, followed by Romney with 26 percent, networks reported. Santorum was in third with 18 percent and U.S. congressman Ron Paul in fourth with 13 percent.
Gingrich contrasted his sometimes-chaotic management style with Romney's buttoned-down approach, arguing that his campaign was powered by ideas rather than logistics.
U.S. television networks declared Gingrich the winner shortly after polls closed at 7 p.m. EST (0000 GMT).
"We have a very real chance on an idea basis as conservatives to offer a better future for the American people. We have an ability to reach out to lots of people and communicate with them without millions of dollars of paid advertising," Gingrich said on Fox Business Network.
"This race is getting to be even more interesting," Romney told supporters.
"We're now three contests into a long primary season," he added in a speech in which he took several shots at Gingrich, including condemning Republican rivals for assaulting free enterprise as they criticized his business resume.
FLORIDA IS NEXT
The next contest is the Florida primary on January 31. It will be the largest state yet in the nomination battle and one that will require the candidates to spend quite a bit of money on advertising.
Romney starts off with a wide lead in the polls in Florida and a distinct edge in logistics and fund-raising, which will be crucial in a state that has 10 separate media markets.
A drawn-out Republican contest would likely help Obama as Republican candidates would continue to spend time and money attacking each other.
Obama, who does not face a primary challenger, will have his turn in the spotlight on Tuesday with his State of the Union address. In a message to supporters on Saturday, he said the speech would focus on "building an economy that works for everybody, not just a wealthy few.
Animosity between Gingrich and Romney has been festering since December, when a group supporting Romney launched a blitz of negative TV ads in Iowa that effectively ruined Gingrich's campaign there.
In South Carolina, a state with a reputation for rough and tumble politics, the gloves came off.
Gingrich attacked Romney's business record and reluctance to release personal tax information, while Romney pointed to Gingrich's past ethics lapses and alluded to his messy personal life.
Voters said they were overwhelmingly focused on fixing the sluggish economy and finding the strongest candidate to defeat Obama. Some 78 percent said they were "very worried" about the economy and 45 percent said that the most important trait in a candidate was the ability to beat Obama, according to exit polls released by CNN.
Those issues are the twin pillars of Romney's candidacy.
Romney had developed an aura of inevitability after strong showings in the first two nominating contests, and he led South Carolina polls by 10 percentage points a week ago.
He suffered a setback on Thursday when Iowa officials declared in a recount that he had come in second place in that state's January 3 contest, behind Santorum, instead of winning narrowly as initially announced.
Romney is among the richest men ever to run for the U.S. presidency and his stewardship of the private equity firm Bain Capital has been criticized by Gingrich and others.
"If Republican leaders want to join this president in demonizing success and disparaging conservative values then they are not going to be fit to be our nominee," Romney told supporters.
Voters said they viewed Romney's business background as an asset. But he waffled this week when asked whether he would release his tax records, and acknowledged that he pays a much lower tax rate than many Americans.
'PUNCH IN THE MOUTH'
"This is the punch in the mouth/wake up call Romney needed if he wanted to be a strong general election candidate," Republican strategist Ford O'Connell said in a Twitter message, referring to the South Carolina results.
Romney attacked Gingrich's ties to mortgage giant Freddie Mac and criticized his time in the nation's capital. His campaign also highlighted Gingrich's $300,000 fine due to ethics lapses while serving as House speaker 15 years ago.
The thrice-married Gingrich has fended off publicity about his turbulent marital history. On Thursday, he rejected his second wife's accusation that he had asked her for an "open marriage" while he was having an affair with another woman in the 1990s.
South Carolina has been a tough state for Romney's presidential ambitions. In his previous run for the White House in 2008, Romney finished a poor fourth, with just 15 percent of the vote, behind winner and eventual Republican nominee John McCain. McCain endorsed Romney in the current campaign.
The winner of South Carolina's Republican presidential primary has gone on to win the party's nomination in every presidential election since 1980.