|Romney, centre, faced criticism from his rivals over his past career as head of a private equity firm [GALLO/GETTY]
Republican US presidential hopeful Mitt Romney came under attack over his business record and his failure to release his tax returns as his rivals set their sights on the front-runner in a televised debate before Saturday's South Carolina primary.
Newt Gingrich, Rick Perry and Rick Santorum on Monday urged voters to take a critical look at the past record of the former Massachusetts governor, who leads the race for the nomination to challenge Barack Obama in November's presidential vote.
Gingrich questioned Romney's role as head of private equity firm Bain Capital, which, critics say, slashed jobs and plundered companies under his stewardship.
"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," Gingrich, the former House speaker. "That's part of what a campaign is about, to answer those questions and deal with them effectively."
"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"
-Newt Gingrich, Republican candidate
Romney, who has already won both the Iowa caucuses and the New Hampshire primary, said the firm had invested in more than 100 businesses. Some had lost jobs, while others thrived and created jobs, he said.
"If people want to have someone who understands how the economy works, having worked in the real economy, then I'm the guy who can best post up against Barack Obama," Romney said.
Perry, the Texas governor who has focused his early campaign on a strong showing in South Carolina, challenged Romney to release his tax returns, something that Romney has so far not agreed to do, although he has not ruled out doing so in the future.
"We need for you to release your income tax so the people of this country can see how you make your money," Perry said.
Romney did not respond to Perry's request.
Al Jazeera’s John Terrett, reporting from Washington, said: "There was almost no unity on the stage, it was really four men dumping big time on Romney. And the last attack from Perry, the current governor of Texas, asking Romney to release his tax records, I think that really rattled him."
"The other candidates are trying to stop him from winning or at least come a very close second to represent the right of the party because Romney is a moderate and Rick Santorum and Newt Gingrich are hoping to pick up votes from the right," he said.
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The candidates also sparred on foreign policy during the debate after Texas representative Ron 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 leader Osama bin Laden rather than kill him in a May 2011 raid.
"I would say that maybe we ought to consider a golden rule in foreign policy," he said, to an eruption of boos from the audience.
"We endlessly bomb these countries and then we wonder why they get upset with us."
Romney hit back, saying: "Of course you take out our enemies, wherever they are. These people declared war on us. They've killed Americans..."
"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."
Perry, meanwhile, in a foreign policy stumble, described Turkey - a key US ally and NATO member - as a state "ruled by what many would perceive to be Islamic terrorists".
Stance on abortion
Monday's debate in Myrtle Beach came hours after Jon Huntsman, the former governor of Utah, dropped out of the Republican race and endorsed Romney, further bolstering his drive for his party's nomination.
The debate is the first of two to be held this week in South Carolina, where a Romney win on Saturday could put him on an almost certain path to clinching the right to challenge Obama in November's election.
Polls show Romney with a solid lead in South Carolina over Gingrich heading into the debate. Another debate will be held in Charleston on Thursday.
"South Carolina is very different from New Hampshire, as it has large population of evangelical Christians who have said they will not vote for Romney, based on his previous stance on abortion and other issues," Al Jazeera's Terrett said.
"However, polls in the state seem to suggest actually evangelical Christians are preparing to coalesce around Romney after all, which is part of his commanding lead."