There are two very different schools of thought on Rick Santorum’s chances of becoming the Republican Party’s presidential nominee. And this week has produced plenty of fresh evidence to buttress both of them.

Santorum supporters point to several polls placing him in the lead in the crucial state of Michigan, which votes Feb. 28 and which Mitt Romney had been almost universally expected to win.

Their broader argument is that Santorum has now exposed Romney’s vulnerabilities, consolidated the support of the GOP’s conservative wing, and has a serious shot at winning the nomination.

{mosads}They also argue that the Friday endorsement of Santorum by former Ohio Sen. Mike DeWine, who had previously backed Romney, was evidence that even seasoned politicos believed the tide had shifted in his favor.

DeWine’s comment that Romney displays “an astounding inability to provide voters with a rationale to support him” further sharpened the impact.

Yet the skeptics argue that Santorum’s focus on social issues makes him unelectable, he is hopelessly outgunned in the battle against Romney, and his chances of success are being ginned up by a news media desperate to confect the sense of a competitive race where none truly exists.

They note that the former Pennsylvania senator had to waste precious time Friday distancing himself from a bizarre comment made the previous day by Foster Friess, the wealthy businessman who has been a key benefactor of the super-PAC that supports him.

Speaking about contraception, Friess told MSNBC, “Back in my day, they used Bayer aspirin for contraceptives. The gals put it between their knees and it wasn’t that costly.”

Santorum told CBS that Friess’s comment was “stupid” but also pushed back against any sense that he should be held in some way responsible.

He told National Review that the idea that “somehow or another Foster Friess is now who I am” was “just crap.”

The question of how Santorum’s own social views play out within the Republican primary is complex, however. Even as his trenchantly conservative beliefs give centrists pause for thought about his electability, they delight a sizable number among the party’s base.

“It plays out at the grassroots level as a significant plus for him in the Republican primary. There is no flip-flopping there at all,” Republican strategist Keith Appell, who is not allied with any of this year’s candidates, told The Hill. “And when that it is seasoned with a Reaganesque approach to stimulating the economy, it is a powerful cocktail for a lot of folks.”

Santorum sought to shift the focus onto economic issues with a speech to the Detroit Economic Club Thursday.

Although the address emphasized his plan to eliminate corporate tax for manufacturers, any advantage that he gleaned in the Motor City may have been neutralized by his reaffirmation that he would have opposed the bailout of the auto industry. Romney rolled out an endorsement from Michigan Gov. Rick Snyder (R) on the same day — taking a good deal of the local spotlight off Santorum.

The day’s events resurrected some doubts about the extent to which Santorum can truly compete with Romney.

“It is very hard to see Santorum getting to 1,144 delegates,” Geoff Skelley of the University of Virginia’s Center of Politics said, referring to the number of delegates required to win the nomination.

“A brokered convention? There is the possibility for that to happen. But it’s difficult to see Santorum actually winning.”

Much will come down to Michigan. A Santorum win would be a colossal blow to Romney. It would also prove that Santorum could stand up to the barrage of negative ads Romney and his allies have already begun to lob at him.

“Romney better pray that the negative ads from the super-PAC work, or he’s got a big problem,” Democratic strategist Bob Shrum told The Hill. “And they might not work. You can only go to that well so many times.”

A win or even a very close second-place for Santorum in Michigan could also have vital knock-on effects, experts say. It would give Santorum a big boost going into Super Tuesday on March 6.

If he did well there, questions would arise as to how long Newt Gingrich could maintain his viability. If Gingrich were to pull out of the race, Santorum would finally have a clean shot at Romney, with no comparable conservative left in the race. (Ron Paul remains, as ever, a case apart.)

Any detour from the optimal path could yet doom Santorum, however. A big win in Michigan for Romney would all but restore the former Massachusetts governor’s aura of inevitability.

Santorum has already come back from the near-dead twice, to win the Iowa caucuses and to chalk up three victories on Feb. 7. If he fades again, a third resurrection is probably beyond him.

Amid all the uncertainty, one thing is for sure: the importance of the Michigan primary is growing by the day.