The Republicans’ gamble that they could ride a backlash against the Obama administration’s efforts to increase the availability of contraception has gone terribly bad. It turns out that most Americans, especially women, agree that insurance companies should have to cover contraception — for example, birth-control pills — in their health insurance plans.One result of this battle has been a record gender gap in the presidential race, with President Obama leading likely Republican nominee Mitt Romney by a huge margin of 57 percent to 38 percent among women registered voters.A recent Gallup poll of swing states has Obama leading by a 2-1 margin among women under 50.Romney will try to narrow this gap in the general election, but it may not be so easy. He is on the record saying that he would like to “get rid of” Planned Parenthood, as well as eliminate federal funding under the Title X program.