LANSING, Mich. – As Tuesday’s Republican presidential primary approaches in Michigan, native Mitt Romney has found himself in a position that he did not initially expect: fighting from behind. Polls in the state show that former Pennsylvania senator Rick Santorum’s once huge lead dwindled over the weekend, but the fact that Santorum once led by as many as 15 points was stunning.

Initially, it was assumed that Michigan — one of the states that Romney won in 2008 — would be a layup for the former Massachusetts governor. Romney was born in Detroit and grew up in the nearby suburb of Bloomfield Hill; his late father, George, was chief executive of the now defunct American Motors, which was based in suburban Detroit, and went on to become the state’s governor from 1963-1969.

George Romney became one of the state’s most popular governors of the last 50 years, helping to improve Michigan’s struggling economy and infrastructure. He was also one of the most prominent Republicans who ardently supported the Civil Rights Movement and desegregation of that era.

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Unfortunately for his son, his father’s cache has not led to an easy win.

“The race has become nationalized,” said Bill Ballenger of Inside Michigan Politics, a newsletter about the state’s politics. “Santorum had no connection to Michigan until last week. He was introducing himself to the state for the first time personally. Nobody in the Republican primary knew a thing about Santorum other than what they’ve seen on tv or heard in the news media.”

He added, “Republican primary voters are smart enough to figure out that with all the other candidates having dropped out of the race, Santorum is the most plausible anti-Romney candidate that’s stayed in the race at this point.”

Santorum, who narrowly defeated Romney in Iowa, was considered an afterthought after finishing far behind Romney and former House Speaker Newt Gingrich in subsequent primaries.

But his sudden victories in Colorado and Minnesota earlier this month propelled him back into the spotlight, and in front of the often-presumed frontrunner Romney in some polls, both in Michigan and nationally.

Public Policy Polling, which showed Santorum had a 15-point lead in Michigan over Romney last week, reported a new survey showing that Santorum’s lead fell to 4 points, 37 percent to 33. The poll shows Rep. Ron Paul of Texas with 15 percent, and Gingrich with 10 percent. Some polls have even shown Romney leading Santorum.

Both Democrats and Republicans in Michigan have harshly criticized Romney for his continued insistence that the 2009 bailout of General Motors and Chrysler was a bad idea and a failure. In 2008, he wrote the now infamous column “Let Detroit Go Bankrupt”, and on Feb. 14, he wrote a piece in the Detroit News, decrying the bailout as “crony capitalism on a grand scale.”

But those views may little impact on this primary, in part because Santorum also opposed the bailout.

“The auto bailout article he wrote in the New York Times, and the one he wrote last week have no relevance to the primary here in Michigan,” Ballenger said.

He added, ”(The bailout) matters to the Democratic voters and to the independents and will be an issue if Romney emerges as the Republican nominee against President Obama. But in this primary, it’s almost irrelevant.”

The poll numbers also bore that out. Thirty-four percent of Republican voters in Michigan said that they were more likely to vote for someone opposed to the bailout. Another 35 percent said the candidate’s stance on the bailout did not matter.

Romney’s struggles here are similar to those nationally, particularly with the GOP’s conservative base.

“This is going on in every state,” Ballenger said. “You can go to Indiana, any state, it’s going to be the same thing. People are saying this in the poll. People are saying it in the conservative wing of the base, the Tea Party, the Christian fundamentalists, and people who are social and cultural conservatives are having a really tough time feeling totally comfortable with Mitt Romney.”

If Romney is able to win Michigan on Tuesday, and eventually capture the nomination, he is still in a tough battle against President Obama. Latest polls show Romney trailing the President 49 percent to 43 percent in Michigan, where a Republican has not won the state since George H.W. Bush in 1988.

“He’d still be an underdog here,” Ballenger said. “Anyone who thinks because Mitt Romney was born in Michigan, and the Romney name has some residual clout, it will probably help Romney if he’s the nominee against Obama, but just not enough for him to win.”

Follow Jay Scott Smith on Twitter at @JayScottSmith