Jonathan Chait states the obvious:

Bush is mainly interested in harvesting votes from religious conservatives in order to implement an agenda dominated by his economic backers. In liberal-ese: Social conservatives are hapless GOP dupes.

I agree, and have for years. In fact, Bush is playing this hand quite shrewdly. The religious right are indeed zombie-like voters, usually basing their entire rationale on one, maybe two, issues, and that's it. If a candidate is against abortion rights and gay marriage then that person is VERY likely to get their vote no matter what they stand for on anything else. If the candidate also supports anti-environmental measures or the NRA or tax cuts for the extremely rich, well that doesn't matter, it's ignored. What counts are those few issues that would seem to insure that the voter is on the side of Jesus. But as I constantly remind, Bush endorsed pro-choice Specter over pro-life Toomey, i.e. politics before supposed principles.

Again, can you blame Bush? He realizes he can continuously stomp on these folks since they have no alternative. What are they going to do, vote for the Satan-loving Democrat? Behind closed doors, he and Rove simply laugh at the fools -- but thank the Lord they exist! As Chait writes, "With allies like these, Bush doesn’t have much incentive to work harder to reward his social conservative base."