DELRAY BEACH, Fla. - A reshuffled Republican presidential race moved to Florida on Sunday for the first big-state primary, with a worried party establishment facing the emergence of the mercurial Newt Gingrich as a serious contender and the possibility of a long and bitter nomination fight.

Gingrich's shocking 12-point victory in South Carolina on Saturday ensured 10 days of furious campaigning before the Jan. 31 Florida primary. The result also punctured Mitt Romney's aura of inevitability and shifted the dynamics of an already turbulent contest.

"I'm happy to be in the tradition of Ronald Reagan as the outsider who scares the Republican establishment," Gingrich, the former speaker of the House, said on NBC's Meet the Press. "And frankly, after the mess they made of things, maybe they should be shaken up pretty badly."

Many party elders worry that the bombastic Gingrich, who has been viewed unfavorably by as many voters as hold him in a more favorable light in recent national polls, would not be able to attract enough independents and disaffected Democrats to be electable in November.

Joe Penkalski, 50, a contractor originally from Erie, Pa., who has lived in Delray Beach for 20 years, does not want Gingrich to be the GOP nominee. "I don't think he'll win here," said Penkalski, who was strolling through an arts festival Sunday. "He is just too overpowering sometimes. He is a no-nonsense guy, but he is too forceful." Penkalski worries that a President Gingrich would keep U.S. troops involved in a Gordian knot of overseas fights.

"So to keep Gingrich out, I'll probably have to go the other way. With Mitt," he said.

Romney has much more money and a better organization than Gingrich in the state, and his aides have built their war plan on the assumption of a drawn-out fight for delegates in multiple state contests. Already, the former Massachusetts governor and his allies have spent more than $7 million on TV ads in Florida, a little more than half of it on spots that attack Gingrich. About 200,000 votes have been cast here by absentee ballot and early voting - most of them while Romney was the one Republican in the field with momentum.

The South Carolina GOP primary has, since its inception in 1980, been where insurgent candidacies go to die, but this time, Gingrich was able to capitalize on two dominating debate performances in the week before the vote. Front-runner Romney was thrown off balance by demands that he release his tax returns, first refusing, then equivocating, then saying he would probably release the information but not until April.

While Romney dealt with those questions, Gingrich kept up the attacks on President Obama - calling him a "food stamp president" bent on building an "entitlement society," for instance. He was able to channel the anger and the deep distaste for the president that has fueled the grassroots in the Republican Party over the last three years.

Florida's primary is closed, meaning it is open only to registered Republicans, unlike the contests in South Carolina, New Hampshire, and Iowa. The state is vast and its population racially and ethnically diverse, with 10 media markets; it costs a minimum of $2 million a week to run TV ads statewide, political strategists say.

Advisers to Romney say that they will keep up the pressure on Gingrich as a creature of Washington with ethical and personal baggage and a reputation as speaker for erratic behavior. Gingrich, meanwhile, wants to portray himself as a bold contrast in comparison with Romney's pale Massachusetts moderate.

Early Sunday, Gingrich and Romney were hammering each other's character and qualifications on the political talk shows.

Appearing on Fox News Sunday, Romney said that Republicans would not nominate someone who, like Gingrich, "spent 40 years in Washington as a congressman and a lobbyist." Gingrich is not a registered lobbyist, but he has worked as a "consultant" to semigovernment mortgage entitiy Freddie Mac.

Romney also questioned Gingrich's "sobriety" and "steadiness." One of Romney's most prominent backers, New Jersey Gov. Christie, attacked Gingrich harshly on Meet the Press.

"He was run out of the speakership by his own party," Christie said. "He was fined $300,000 for ethics violations. This is a guy who's had a very difficult political career at times and that has been an embarrassment to the party."

Romney has plenty of advantages, but momentum is important, too.

"Now the question becomes: Does he get back on message for where the campaign is going in the fall," said Alan Novak, former chairman of the Pennsylvania GOP and a businessman who is supporting Romney. "Until South Carolina, Romney was able to stay on the main themes of the election - jobs and economics - and to talk about the weaknesses of this administration."

Rick Santorum, who finished third in South Carolina, fought the notion that the race had narrowed to a two-man battle. Speaking on ABC's This Week, he said that Romney was not a conservative at all and that Gingrich was not a consistent one. "That's not a choice between a conservative and a moderate, it's a choice between a moderate and an erratic conservative, someone who, on a lot of the major issues, has been just wrong," Santorum said.

On Sunday, Romney announced he would release his tax returns Tuesday on the Internet, for 2010 and an estimate for 2011. Supporters such as Novak breathed a sigh of relief.

Meanwhile, in Florida, gynecologist Harold Wittcoff of Boynton Beach said he cast his absentee ballot for Romney a month ago. "I don't like to wait at the polls," he explained, and he did not see the need to wait for the campaign to evolve further. "You decide who is the candidate you like and that's it," said Wittcoff, 68, a North Jersey native. "I am not going to change my mind based on everybody's cruel comments."

He said he liked Romney's experience in business. "We need a competent business person who understands the ups and downs of capitalism to run the economy," Wittcoff said.