To be honest, I won't be surprised if Bush just said 'The jury's still out there' for the hardcore Christian votes, while knowing that the people who believe in evolution won't change their votes against Bush just because of evolution, but hardcore christians might.
I agree with most of the posters that this isn't a good idea. While I think our Presidents should be literate in science I don't think they need expertise and even if they were I fear that the narrow focus that science often demands might blind them to many other things. The best quality we need in our President is wisdom which means being able to listen and act on the information he / she is getting from scientists and others. I don't think we have that currently but I am not really sure how we can find that out ahead of time, especially in a debate format.
Just checking in on this thread and noticed your post... flaw in your sig is line 3. EDIT: to be precise, it's lines 3 and/or 4, depending on your POV.