To “the dog ate my homework,” we can now add “my wife wrote the chapter.”

That’s the excuse, more or less, with which Rick Santorum is distancing himself from a snippet of his 2005 book, “It Takes a Family,” in which “radical feminists” are disparaged for giving women the idea that they might find greater fulfillment outside the home. By using the passive voice in the last stretch of that sentence, I’m cutting him a break. I could have said “he disparaged” those feminists, because he’s the only author listed on the book’s cover, and there’s no acknowledgment of literary assistance from the hard-typing, home-schooling, house-tethered missus. So even if he’s not a troglodyte, he’s something of a credit hog.

You gotta love politics, and you gotta love Santorum. For much of this campaign, he has been content to occupy the rightward extremes of social issues, where he obviously felt he would best find traction. For most of last week, he stood there proudly and loudly, championing the Roman Catholic bishops in their archaic — and, let’s be clear, irresponsible — antipathy to birth control.

He even came up with perhaps the most ridiculous hyperbole in a political season thick with it. He said that “the path of President Obama and his overt hostility to faith” would lead the country to “the guillotine,” an apparent assertion that for Obama, hope and change are the smokescreen, deficits and decapitation the real agenda.

Given all of Santorum’s regressive bluster, why should he suddenly evince alarm over seeming to be out of touch with the aspirations, emotions and rights of women? What’s changed? The polls, for one: two new Michigan surveys show him ahead of Mitt Romney there. And his tally of victories rose last week from one (Iowa) to four (if you count Missouri). Once preposterous, his candidacy is newly plausible, giving him fresh motive to blunt some of his divisive edges. Nothing rewrites the past like pumped-up designs on the future.