Frank Rich writes: At the time, back in January in New Hampshire, it didn’t seem like that big a deal, certainly nothing to rival previous debate flash points like “9-9-9” and “Oops!” But in retrospect it may have been one of the more fateful twists of the Republican presidential campaign. The exchange was prompted by George Stephanopoulos, who seemingly out of nowhere asked Mitt Romney if he shared Rick Santorum’s view that “states have the right to ban contraception.” Romney stiffened, as he is wont to do, and took the tone of a men’s club factotum tut-tutting a member for violating the dress code. “George, this is an unusual topic that you’re raising,” he said. “I know of no reason to talk about contraception in this regard.” The partisan audience would soon jeer the moderator for his effrontery.

Afterward, Romney’s spokesman Eric Fehrnstrom accused Stephanopoulos of asking “the oddest question in a debate this year” and of having “a strange obsession with contraception.” It was actually Santorum who had the strange obsession. He had first turned the subject into a cause in October by talking about “the dangers of contraception in this country.” Birth control is “not okay,” he said then. “It’s a license to do things in a sexual realm that is counter to how things are supposed to be.”

As we know now, Santorum, flaky though he may sound, is not some outlier in his party or in its presidential field. He was an advance man for a rancorous national brawl about to ambush an unsuspecting America that thought women’s access to birth control had been resolved by the ­Supreme Court almost a half century ago.

The hostilities would break out just weeks after the New Hampshire debate, with the back-to-back controversies of the White House health-care rule on contraceptives and the Komen Foundation’s dumping of Planned Parenthood. Though those two conflicts ended with speedy cease-fires, an emboldened GOP kept fighting. It had women’s sex lives on the brain and would not stop rolling out jaw-dropping sideshows: an all-male panel at a hearing on birth control in the House. A fat-cat Santorum bankroller joking that “gals” could stay out of trouble by putting Bayer aspirin “between their knees.” A Virginia governor endorsing a state bill requiring that an ultrasound “wand” be inserted into the vagina of any woman seeking an abortion.