COLUMBIA, S.C. (AP) — Next up, South Carolina. And it's shaping up to be a dogfight.

The Republican presidential race turns to this state Wednesday as Mitt Romney's rivals set their sights on trying to tear down the GOP front-runner.

A rougher tone and a tougher ideological terrain await the former Massachusetts governor, who is looking to force his opponents from the race with a four-state win streak that cuts through South Carolina on Jan. 21 and Florida 10 days later. He posted a double-digit win Tuesday night in New Hampshire after a squeaker the week before in Iowa — making him the first non-incumbent Republican in a generation to pull off the back-to-back feat.

"Tonight we celebrate. Tomorrow we go back to work," Romney told a raucous victory party in Manchester, N.H., probably mindful of the minefields that South Carolina held for him four years ago when he failed to win over Republicans skeptical of his Mormon faith and reversals on some social issues. "We are asking the good people of South Carolina to join the citizens of New Hampshire."

With just 10 days before this state's primary, Romney has a target on his back as five others work to emerge as his chief challenger by wooing tea party and religious conservatives who now dominate the GOP here.

All the candidates planned to campaign in the state Wednesday. Romney, former House Speaker Newt Gingrich, ex-Pennsylvania Sen. Rick Santorum, Texas Rep. Ron Paul and former Utah Gov. Jon Huntsman were flying in from New Hampshire. They'll join Texas Gov. Rick Perry, who didn't invest much time in New Hampshire while putting his post-Iowa focus on South Carolina.

Several of Romney's rivals have made it clear that they will seek to undercut the chief rationale of his candidacy: that his experience in private business makes him the strongest Republican to take on President Barack Obama on the economy in the fall. Perry, for one, is accusing Romney of "vulture capitalism" that led to job losses in economically distressed South Carolina.

TV ads already are filling the airwaves, including negative spots like the new one from Gingrich assailing Romney for switching his position on an issue that resonates strongly with evangelicals who make up the base of the GOP here.

"He governed pro-abortion," the Gingrich ad says. "Massachusetts moderate Mitt Romney: He can't be trusted."

About $3.5 million already has been spent on TV ads in South Carolina, the bulk of it by Perry and a supportive super PAC. But that doesn't count the $3.4 million a pro-Gingrich group has pledged to spend to go after Romney, or the $2.3 million a pro-Romney group plans to spend in the coming days. Santorum and a super PAC friendly to him also are pouring money into the state, as is an outside group working on Huntsman's behalf.

Expect a flood of more hard-hitting commercials — primarily aimed at the front-runner — in a state known for brass-knuckled Republican politics.

Romney, for his part, is dismissing the attacks, most notably the ones over his time at Bain Capital.

"President Obama wants to put free enterprise on trial. In the last few days, we have seen some desperate Republicans join forces with him," Romney said in his victory speech, chastising his critics while acting as though he is already the nominee. "This is such a mistake for our party and for our nation."

"The country already has a leader who divides us with the bitter politics of envy," Romney added.

For all of Romney's challenges, the presence of a cluster of socially conservative candidates fighting to be his chief alternative could work in his favor by splitting the vote on the party's right flank. Santorum, Gingrich, Perry and others split the faith-focused vote in Iowa. South Carolina also has a large contingent of evangelical voters, some of whom remain suspicious of Romney.

Unlike New Hampshire, South Carolina could end up being the last stop for some candidates.

Perry, for one, has had back-to-back dismal showings, and is dismissing the earlier contests as inconsequential as he looks to right his struggling campaign in South Carolina.

"They kind of start separating the wheat from the chaff, if you will," Perry told a cafe crowd Tuesday. "But South Carolina picks presidents."

Gingrich, the former Georgia lawmaker, is also playing on his regional ties.

"The ideal South Carolina fight would be a Georgia conservative versus a Massachusetts moderate," he said, echoing a theme central to his fierce ads.

Santorum and Huntsman also have vowed to press on in the face of Romney's latest victory. Santorum wants to claim the conservative mantle; Huntsman eschews ideological labels and is selling himself as someone who can heal a polarized nation.

"Third place is a ticket to ride, ladies and gentleman," Huntsman boomed from the lectern after finishing third in New Hampshire. "Hello, South Carolina."

But Chip Felkel, a veteran GOP strategist in South Carolina who aided the campaigns of both Bush presidents, said before Tuesday's vote that a convincing Romney win would make him hard to stop. Felkel, who remains neutral, predicted voters on the fence will break Romney's way.

"The air of inevitability does kick in and a lot of those undecideds will want to go with the guy who's perceived to be the one to get the nomination," Felkel said.

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