LAS VEGAS - Republican presidential contenders piled on the two front runners, attacking businessman Herman Cain's economic plan as a tax increase and former Massachusetts Gov. Mitt Romney over his healthcare law.
Rep. Michele Bachmann of Minnesota led the assault Tuesday night, saying Cain's call for a 9 per cent federal sales tax would only be the beginning, with the rate rising later.
Former Sen. Rick Santorum cited one analysis that found that taxes would go up for 84 per cent of American households under the plan.
Texas Gov. Rick Perry and former Sen. Pennsylvania Rick Santorum tag-teamed Romney over Massachusetts' health care law that Democrats used as a model for their national health care plan.
Perry said Romney is being dishonest about his record on the law, while Santorum was more direct: "You just don't have credibility, Mitt."
Romney defended his plan as right for his state but wrong for the nation.
Cain, for his part, insisted the charges about his tax plan were untrue and that he was being criticized because lobbyists, accountants and others stood to benefit from the current tax code.
Cain has never held public office, but has built up a following among conservative activists as a radio talk show host and motivational speaker. That background has boosted his popularity with his poll numbers having jumped to put him in a dead heat with the presumed front-runner, former Massachusetts Gov. Mitt Romney.
All are vying for the Republican nomination to challenge Democratic President Barack Obama in 2012, and many undecided voters have been watching the debates to evaluate the candidates.
Much of the focus Tuesday has been on Cain's catchy "9-9-9" tax overhaul plan which he's made the centerpiece of his campaign. The plan would scrap the current tax code and replace it with a 9 per cent tax on personal income and corporations as well as a new 9 per cent national sales tax.
The backdrop for the debate was the state's the 13.4 per cent unemployment rate, the country's highest. The formerly fast-growing neighbourhoods north of the glittering Las Vegas strip are now wracked by foreclosures.
Texas Rep. Ron Paul and former House of Representatives Speaker Newt Gingrich of Georgia are also taking part in the debate.
Former Utah Gov. Jon Huntsman, also widely considered a moderate, was boycotting the debate and the Nevada caucuses in a dispute over the Republican primary calendar. Nevada has scheduled its contest for Jan. 14, and Republican officials are pressuring Romney and other Republicans to join Huntsman's boycott if the state refuses to hold the caucuses later in the month.
Romney has so far refused to join the boycott, though the New Hampshire primary, traditionally the nation's first, is a must-win contest for him. In a conference call with New Hampshire supporters before the debate, he reassured Republicans there that he sees their primary as important.
Romney also used the call to attack Cain over his "9-9-9" tax plan.
"Most people in middle income categories will have their taxes go up" under that plan, Romney said in the call, and he said senior citizens would be hurt.
In that, he and Democratic President Obama agree. In an interview with ABC News, Obama said Cain's tax plan would be a "huge burden" on middle-class and working families.
Obama's campaign -- increasingly focused on Romney as the likely Republican nominee -- responded immediately. "Mitt Romney's message to Nevada homeowners struggling to pay their mortgage bills is simple: You're on your own, so step aside," spokesman Ben LaBolt said.
