Mitt Romney has emerged largely unscathed in the latest debate among a shrinking field of Republican hopefuls launching attacks on his moderate political record and career in venture capitalism.
Mr Romney's four opponents went on the attack from the outset, trying to prove he is not up to the coming battle against President Barack Obama.
With unemployment still high, the national debt at worrisome levels and millions of voters having lost their homes to mortgage foreclosures, the Republican candidates are fighting fiercely to carry the party banner against Mr Obama's perceived weakness.
The first of two debates before the pivotal South Carolina primary election on Saturday, produced the most vigorous give-and-take of the more than a dozen such meetings. While the multi-millionaire Mr Romney largely stood his ground unshaken by assaults on his record, he was cornered on the issue of revealing his tax returns.
He agreed to decide on allowing voters to examine those tax documents in April, the month when all Americans are required to file tax reports with the federal government.
Candidates for high office in the United States routinely make their tax filings available to the public as a good-faith effort to show their sources of income and assessments paid to the government. There has been broad speculation that Mr Romney, while paying taxes as required, does so at a rate much lower than that assessed on the wages of average working people. US law allows investors such as Mr Romney to pay a considerably lower rate on income from capital gains. Other loopholes available to financiers offer substantial deductions.
The debate came hours after Jon Huntsman withdrew from the race and endorsed Mr Romney. That left him still confronting Newt Gingrich, Rick Santorum, Rick Perry and Ron Paul. Polls show Mr Romney, the former Massachusetts governor, as the clear favourite in conservative South Carolina despite the mistrust or ambivalence of Republican voters who are unhappy with his past stands on social issues like abortion.
Mr Gingrich has virtually conceded that a victory for Mr Romney in the first-in-the-South primary in South Carolina would assure his nomination.
But Mr Gingrich and Mr Perry, the governor of Texas, were on the attack against Mr Romney's greatest perceived vulnerability, his record at Bain Capital, the private equity firm that bought companies and sought to remake them into more competitive enterprises.
"There was a pattern in some companies ... of leaving them with enormous debt and then within a year or two or three having them go broke," Mr Gingrich said. "I think that's something he ought to answer."