On another point, Cain felt it necessary to make a post-debate apology to House Democratic leader Nancy Pelosi, whom he had called "Princess Nancy" for sidetracking Republican legislation when she was speaker.
The announced topic for the evening was the economy, a subject that produced few if any early sparks among rivals who often spar energetically.
Perry, Gingrich, Bachmann and former Pennsylvania Sen. Rick Santorum joined Romney, Cain, Paul and Huntsman on stage at Oakland University in Michigan, a state where unemployment is 11.1 percent and well above the national 9 percent jobless rate.
The debate took place less than two months before Iowa's kickoff caucuses, as the pace of campaign activity accelerates and public opinion polls suggest the race remains quite fluid. Romney and Cain currently share co-front-runner status in most surveys, with Perry and Gingrich roughly tied for third, within striking distance.
Not surprisingly, none of the contenders found much to like in Obama's economic stewardship.
Perry said the next president should systematically judge all of the government regulations enacted since Obama took office on a standard of whether they created jobs. Any that failed should be repealed, he said.
Bachmann sharply criticized Fannie Mae and Freddie Mac. She said the latter had recently given multimillion-dollar bonuses to executives even though it was seeking a new federal bailout.
Gingrich, who last held public office more than a decade ago, bristled when asked what advice his company had given Freddie Mac for a $300,000 fee. "Advice on precisely what they didn't do," he shot back — stop backing mortgages to applicants who aren't credit-worthy.
The government rescued mortgage giants Fannie Mae and Freddie Mac in September 2008 to cover their losses on soured mortgage loans. Since then, a federal regulator has controlled their financial decisions.
The cost to taxpayers so far has been about $169 billion, the most expensive bailout of the financial crisis.
There was only scant mention of the Michigan auto industry, which benefited in 2008 and 2009 from a federal bailout that both President George W. Bush and Obama backed.
All eight Republicans on the debate stage say they wouldn't have offered government assistance.
Not so Obama, who stood outside a factory not far from the debate site recently and said government bailouts of General Motors and Chrysler were a success that saved thousands of American jobs.
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