Maybe anyone who voluntarily runs the gantlet we call our presidential election process must be mentally imbalanced in some respect, but this year’s crop of Republican candidates has been especially odd.

Of the four who remain viable, only Mitt Romney can even pass as normal -- and he has that eerie, Stepford-wife quality of being so normal it’s weird.

Upon first exposure, it doesn’t take long to identify Ron Paul as a charming old crank, or Newt Gingrich as an egomaniac who imagines that the voices he hears in his head are the calls of destiny. Rick Santorum is, at first, harder to characterize.

Along with Paul, he ranks high on the sincerity scale. But whereas Paul has an appealing innocence that takes the form of true puzzlement at why everyone doesn’t agree with him, Santorum is generally solemn, almost sad-looking, and usually humorless. When complaining about some Obama administration betrayal of all human decency, he comes off sounding more like a sulky teenager arguing some irritating point of principle than the tribune of the working class that he would like to be.

Remarkably Mild-Mannered

For a man going after Pat Buchanan’s old constituency, Santorum is remarkably mild-mannered. The worst you can say about his public personality is that he’s cute when he’s mad. Buchanan, who was fired last week by MSNBC, isn’t. (Apparently, the network discovered, after using him as a commentator for a decade, that Buchanan is an unacceptably extreme right-winger with controversial racial and ethnic views.)

Perhaps Santorum will inherit Buchanan’s seat as token conservative at the network that recently gave Al Sharpton a show. For a long time after Santorum announced his candidacy for president, nobody paid him much attention, under the assumption that his real goal was his own TV show, or at least higher fees for public speaking, when he inevitably dropped out of the race.

After all, his most recent political achievement was losing his Senate seat in Pennsylvania to a Democrat by 17 points six years ago. If everyone with a political record no better than this had to be taken seriously when he or she announced a run for president, the field would be crowded indeed.

But it turns out the little voice that tells some of the most unlikely people, “You know, you could be elected president,” was telling Rick Santorum the truth. In some polls, he is leading Romney in Romney’s native state of Michigan, though the gap is narrowing. So the news media are only now discovering that Santorum is more than just another ugly face.

Metaphorically, that is: Physically, he is boyishly pleasant-looking, though not handsome in the Romney central-casting way. Frankly, he looks less like the president than any of his remaining Republican rivals. The coating of gravitas that automatically gets applied to those who hold the job will have to be applied especially thick if Santorum should win.

Unlike Romney, Santorum is a man of principle. But what principles! He’s an absolutist on abortion, wanting it banned even in cases of rape and incest. Over the weekend he said that not just the federal government but also state governments should keep their noses out of public education. Same-sex marriage? Guess.

Santorum has been best known for his stark right-wing views on social issues and his unyieldingly pugnacious legislative style when he was in office. Now people are looking into his economic views. The noteworthy thing about these is how little he bends the standard right-wing pro-business litany to accommodate his special sympathy for the working stiff. He favors new tax breaks for everything from small business to large families. He promises to cut a trillion dollars from federal spending every year for the next five years. Details still to come, of course, except that he would freeze entitlement spending.

Like most politicians who talk a good capitalist game, Santorum is a free trader in theory and a protectionist in practice. But, oddly, so is Romney. In fact, the need to rein in China -- that is, to stop Americans from buying Chinese products they wish to buy at prices they wish to pay -- is just about the only subject that brings out seemingly real passion in Romney.

A Brazen Appeal

The Michigan primary, coming Feb. 28, will tell us whether Romney is invincible or all too vincible. Both Santorum and Romney say they wouldn’t have bailed out the auto industry. Santorum told the Detroit Economic Club last week that the difference between him and Romney is that he wouldn’t have bailed out the finance industry either. (Romney supported the bank bailout.) Perhaps it’s just schadenfreude, and auto workers don’t mind being laid off as long as bankers are laid off too.

But this brazen appeal to logical consistency -- not normally a big vote getter in American politics -- surprisingly seems to be working.

(Michael Kinsley is a Bloomberg View columnist. The opinions expressed are his own.)

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To contact the writer of this article: Michael Kinsley at mkinsley@bloomberg.net.

To contact the editor responsible for this article: Timothy Lavin at tlavin1@bloomberg.net.