In the latest blow to Mitt Romney's aura of inevitability, two Republican presidential polls have Rick Santorum outperforming Mitt Romney in his home state of Michigan.

A telephone poll conducted by American Research Group, Inc. found Michigan voters favoring Santorum over Romney, 33 to 27. Romney fared even worse against self-identified Republican voters and Tea Party supporters, trailing both Santorum and Newt Gingrich in both categories. Romney outpaced Santorum among female voters and had a wide margin of support from independents.

A Public Policy Polling survey found Santorum defeating Romney by an even broader margin of 39 percent to 24 percent. Santorum enjoyed a far greater favorability rating than Romney in that poll, reflecting an enduring problem for Romney -- in a previous ABC News/Washington Post poll, respondents said by a 2 to 1 margin that they liked Romney less the more they learned about him.

The Romney campaign is trying hard to fend off a late surge from Santorum, who registered convincing victories in Missouri, Minnesota and Colorado, and a Michigan loss could be devastating. Romney's father George was governor of Michigan during the 1960's, and Romney has led in polls there all year. He also won the state during his unsuccessful 2008 primary run.

While Romney's campaign has hoped his economy-focused message will resonate in Michigan, Romney's past stances on the auto industry could be a liability. He opposed the bailout credited with helping to resuscitate the ailing sector, in 2008 penning a New York Times op-ed entitled Let Detroit Go Bankrupt.

If General Motors, Ford and Chrysler get the bailout that their chief executives asked for yesterday, you can kiss the American automotive industry goodbye, Romney wrote. It won't go overnight, but its demise will be virtually guaranteed.

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