Just a comment from someone on the left. If the GOP starts to openly question some of the issues that that just cater to the extremes on the right while scaring off the moderates you might be pick up some votes. You can keep the core beliefs, and reject the ID stuff, maybe moderate the AGW rants for example.
Of course, the left should reject some of the Polosi like positions and the like too. We’ll always have clear choices, but both parties could clean up their fringes.