AFP CHARLESTON (SOUTH CAROLINA) REPUBLICAN presidential hopefuls on Tuesday barnstormed South Carolina in a last-gasp bid to prise the party’s nomination from the tightening grip of frontrunner Mitt Romney.

Ahead of the state’s makeor- break vote on Saturday, Romney got another boost with a new poll showing he has pierced the important 30 percent threshold of support among Republicans nationally for the first time.

The ex-Massachusetts governor, who survived unscathed from a bruising debate on Monday, now enjoys the backing of 37 percent among Republicans across the country in his campaign to be the party’s presidential candidate, the Gallup poll said.

“History suggests that Romney is now the probable favorite to win the Republican nomination,” Gallup said, adding his nearest rivals, former House speaker Newt Gingrich and ex-senator Rick Santorum, were polling at 14 percent.

Flush from his victories in the Iowa and New Hampshire contests, such figures would suggest Romney is managing to woo over key evangelical and conservative voters long mistrustful of his credentials and Mormon faith.

In South Carolina, Romney has also pulled ahead of the pack with a two-digit lead as he seeks the party’s crown to take on a vulnerable Democratic President Barack Obama, who will be battling for a second term in the November elections.

Just hours after the debate —when Gingrich renewed his attacks on Romney over his record as head of a company called Bain Capital blamed for bankrupting companies and slashing jobs — the candidates were back on the stump again.

Only five presidential hopefuls still remain after former US ambassador to China, Jon Huntsman, quit on Monday, and all eyes will be on who will be felled next with pressure building on Texas Governor Rick Perry.

Perry had leap-frogged to the front of the pack early in the race, but his bid soon wilted amid a series of gaffes, and even some of his supporters are now urging him to step aside to allow conservatives to coalesce.

The candidates get a final chance to try to dent Romney’s air of invincibility before Saturday’s primary at the next Republican debate in Charleston on Thursday.

A Tuesday poll from Monmouth University showed Romney at 33 percent in the state, ahead of Gingrich’s 22 percent, Santorum’s 14 percent and congressman Ron Paul’s 12 percent. Perry was trailing with six percent.

A win in South Carolina would mark a hat-trick for Romney and most likely seal the deal ahead of the next party primary in Florida on January 31. Romney is already polling way ahead in the Sunshine State with 41 percent support, leaving Gingrich trailing on 26 percent.

Gingrich sought to level the playing field in Monday night’s debate challenging Romney on his business record and suggesting he was unfit to take on Obama in November.

“There was a pattern in some companies, a handful of them, with leaving them with enormous debt, and then within a year or two or three having them go broke. I think that is something he ought to answer,” Gingrich charged.

“We need to satisfy the country that whoever we nominate has a record that can stand up to Barack Obama in a very effective way.” Romney hit back, defending his “record of success” in the private sector, and arguing his business and managerial acumen makes him the best able to defeat Obama and revive the sluggish US economy.

He also reserved his harshest criticism for Obama, accusing the president of trying to turn the United States into a “European social welfare state.” Gingrich meanwhile defended his characterization of Obama as “the food stamp president” when a debate moderator questioned whether it was belittling to poor Americans and minorities. He also stirred up a rare standing ovation from the audience when he defended his idea of employing poor children as public school janitors.

“They’d learn to show up for work. They could do light janitorial duty... They’d be getting money, which is a good thing if you’re poor.

Only the elites despise earning money,” he said.

The candidates sparred on foreign policy after Paul — a staunch opponent of foreign aid and military intervention — suggested Washington should have worked harder with Pakistan to track down and arrest Al-Qaeda chief Osama bin Laden rather than kill him in a May 2011 commando raid.

“I would say that maybe we ought to consider a golden rule in foreign policy,” he said, to a roar of boos from the audience. “We endlessly bomb these countries and then we wonder why they get upset with us.” Romney fired back, saying: “The right thing for Osama bin Laden was the bullet in the head that he received. That’s the right thing for people who kill American citizens.”