Charles Babington

MARQUETTE, MICH.: The question of whether Mitt Romney is conservative enough to deserve the Republican presidential nomination regained center stage in the GOP contest Sunday, with Rick Santorum saying the former Massachusetts governor fails the test.

Santorum urged Michigan voters to turn the race “on its ear” by rejecting Romney in Tuesday’s primary in his rival’s native state, where Romney is spending heavily to avoid an upset.

Santorum said Romney’s record is virtually identical to President Barack Obama’s on some key issues, especially mandated health coverage, making him a weak potential nominee.

“Why would we give away the most salient issue in this election?” an impassioned Santorum asked more than 100 people in a remote, snow-covered region of Michigan’s Upper Peninsula. Santorum, a former senator from Pennsylvania, said he is the true conservative on fiscal and social issues.

Romney rejected the claims.

“The biggest misconception would be that I’m a guy that comes from Massachusetts and therefore I can’t be conservative,” Romney told Fox News Sunday. In his one term as Massachusetts governor, he said, he balanced budgets, reduced taxes, enforced immigration laws, “stood up for traditional marriage” and was “a pro-life governor.”

“I’m a solid conservative,” Romney said.

The exchanges highlighted the choice facing Republican voters Tuesday in Arizona and Michigan, and another 10 states a week later.

Romney took a detour Sunday to the Daytona 500 in Florida, where he talked with fans. Asked whether he follows the sport, Romney said, “Not as closely as some of the most ardent fans, but I have some great friends that are NASCAR team owners.”

Romney said he toured a garage with Richard Childress, who was a championship driver in the 1980s and now owns his own team.

Conservative activists dominate the GOP primaries. But party regulars fear too much focus on the Republican right will leave the eventual nominee poorly positioned to confront Obama in November, when independent voters will be crucial.

Santorum, a hero to anti-abortion and home-schooling advocates, disputes that argument. The way to beat Obama, he said Sunday, is with an unvarnished conservative whose views dramatically clash with the president’s on the economy, church and state, energy, foreign policy and other issues.

He said the party needs “someone who can paint a very different vision of the country.”