I don't really see a lot of difference in the outcome to be honest. No Republican was going to win in this evironment. I know that Schwarzenegger is a moderate, and he is generally percieved as such, but in order to win the nomination he would have had to have tacked to the right just like John McCain did. Tacking to the right, means that he would have had to endorsed many of George Bush's policies. In this end, the best case for Schwarzenegger with all other things being equal is the following map:
Perhaps Schwarzenegger being percieved as slightly more moderate than John McCain enables him to hold Indiana and North Carolina. However, I think Arizona would have flipped had any Republican other than John McCain been on the ticket. And while Schwarzenegger could have perhaps made California marginally competitive (i.e. it would have probably been listed as a lean Democratic state rather than a solid Democratic state thoughout most of the campaign), not even Schwarzenegger coudl have carried California for the Republicans this year.
