About half of the coalition that elects republicans are Evangelical Christians. If your thought is that Evangelicals should show up every four years and vote for those parts of the Republican platform that you support and then quietly slink off and shut up with respect to the parts of the Republican platform that they support, that is not a coalition. You have to face the reality that, eventually, the Republican party is going to have to listen and respond to the desires of Evangelicals--or Evangelicals will have no reason to vote Republican.
The real test is coming up. Will Bush nominate and will the Republican Senators have the guts to confirm only original intenters to the US Supreme Court. My guess is no. At that point the coalition will begin to break apart.
Maybe that's how you feel. I am a rock-rib, pro-life, evangleical, Bible-believing Christian. I have been Republican for years and see no reason to change parties. In fact, This party is all together different than it was 30 years ago during the Nixon/Ford era. Reagan changed the party from its dominant pro-business, country club image to one that has not abandoned its pro-business stance but also supports the lives of the unborn.
Change "Evangelicals" to "social conservatives" -- in order to include the ever-increasing number of conservative and conservative-leaning American Jews -- and you'll have it exactly right! :)