Is Bush truly a devout Christian?

Pennsylvania will have its Republican primary next week and challenger Pat Toomey has reportedly closed Arlen Specter's lead to just 5%. Bush has endorsed Specter. Leaving aside the fact that the collapse in Specter's lead despite Bush's backing speaks volumes about Bush's reduced clout, it occurred to me that the main stance separatinging the two candidates is the issue of abortion. Specter is pro-choice, Toomey is pro-life.

I could be wrong, but if Bush is a self-proclaimed born-again big-time Christian, and he's been an extremely popular figure for the pro-life wing of the Republican Party, than why is he endorsing the pro-choice candidate? Unlike any other political issue, abortion is hot-button and I had always thought by definition it left very little room for compromise. Those on the pro-life side typically invoke religious belief as their #1 supporting argument. The Bible or God says it is wrong -- end of story.

If that is true, apparently Bush is only pro-life when it is politically favorable to be pro-life. In this case, he (and Karl Rove) have found it to be a smarter move politically to back the pro-choice candidate. What does this say about Bush's credentials as a devout pro-life Christian? Why aren't other Republican pro-life Christians speaking out about this seemingly perverse endorsement? Doesn't this further portray a president that will say one thing (and not mean it), but then do another?