Rick Santorum might defeat Mitt Romney in the Michigan primary next Tuesday. It’s worth dwelling for a second on how insane this is. Mitt Romney spent his entire pre-college life in Michigan. He was born in Detroit and grew up in Bloomfield Hills. His father was first the Chief Executive Officer of American Motors, and as such was a major public figure in the state, and then governor for six years. His brother is active in state Republican politics, having run for Attorney General in 1998.

And Romney won the state by nine points in 2008, despite John McCain having bested him in New Hampshire the previous week. Michigan, along with Massachusetts and Utah (where he can count on heavy Mormon turnout), is one of the states that it just makes no sense for Romney to lose.

But as of this writing, the polls show Santorum beating Romney by an average of five points. The New York Times’ Five Thirty Eight blog gives Santorum a 57 percent chance of victory. I’m still in the camp that thinks a Santorum nomination is basically impossible. To nominate a candidate whose last election ended in a 20-point landslide loss as an incumbent would be an unprecedented act of electoral suicide. Political scientists tell us that primaries are decided, ultimately, by party elites, and I think the elites in question fear a Santorum win enough to stop it from happening.

But I also agree with the anonymous GOP senator who’s been telling reporters that if Romney loses Michigan, another candidate needs to enter the race and force a brokered convention. If Romney loses what’s essentially his home state, he can’t be taken seriously as a nominee.

That, too, would be a disaster without much precedent, and it’s worth asking how the GOP got itself caught in this bind. Focusing on any one factor would be a mistake. It’s true that Romney just isn’t a very exciting candidate, that Santorum is more charismatic, and that for socially conservative primary voters, the notoriously anti-gay and anti-birth control Santorum is more appealing than the man who once told an LGBT newspaper that he’d be better than Ted Kennedy on gay and lesbian issues.

But in Michigan specifically, Santorum’s relative success may owe to something stranger: he’s running to Romney’s left on economic issues.

While both Romney and Santorum opposed the auto industry bailout that saved Detroit’s manufacturing sector, Santorum has taken issue with the fact that Romney supported the bank bailouts that happened around the same time.

“Governor Romney supported the bailout of Wall Street and decided not to support the bailout of Detroit,” Santorum said. “My feeling was that we should not support — the government should not be involved in bailouts, period.” The implication is clear: Romney will bail out big finance, but not auto workers. Santorum may not help anybody, but at least he doesn’t treat the little guy worse.

Even more jarringly, Santorum has spoken enthusiastically about unions, saying, “I have no problem with private sector unions” and recalling his grandfather’s membership in a coal miner’s union. In a way, this isn’t too surprising. Santorum, after all, spent two terms as a senator from Pennsylvania, a state where unions have a substantial presence and where catering to industrial interests is the only way to get elected. He voted against a national right-to-work law (which would ban union-only workplaces) and pushed repeatedly for tariffs and other union-backed protectionist measures to help the U.S. steel industry.

And, more generally, Santorum represents a kind of Republican who should be anathema to libertarian-leaning Tea Party types. He backed all manner of major government programs in the Bush years, including the Medicare prescription drug benefit and No Child Left Behind. He was skeptical of free trade, voting against The North American Free Trade Agreement while a member of the House. He said he was “proud” of his record of securing earmarks. When faced with a choice between endorsing fellow Senator Arlen Specter — who would, five years later, become a Democrat and support the stimulus and health care reform — and economically conservative Representative Patrick J. Toomey, Sr. in a Senate primary, he backed Specter.

Santorum was, in other words, everything wrong with Bush-era Republicanism, according to the prevailing narrative among Tea Partiers. Against a guy like Romney, who seems positively giddy when attacking unions or defending the rights of corporations, that should be a death sentence.

In fact, not only has it not killed Santorum so far, but it may also even be helping him in economically depressed and union-friendly Michigan. And if even Republican primary voters are responding well to a guy with that message, it could mean that the past two years’ sharp right turn in economic policymaking is more of a blip than a realignment.

Harvard Crimson, Harvard U. via UWIRE