One word: fundies.
Historically, fundamentalist Christians have not generally either been particuarly conservative or particularly Republican. They began to associate with the GOP in droves in the 1970s, after the Dems thought they now had large enough coalition to shed their embarrassing Southern Rump. Problem is, unlike in the seventies, when the Dems had huge majorities in the House and Senate, and thought they could afford to lose the fundamentalists, the GOP's majority is wafer thin, so they've got to kow-tow to fundamentalists and hope they won't alienate secular conservatives, libertarians and moderates. I think the upcoming election is going to prove this a miscalculation.
Christophobia