However, I think this will probably be a positive for many people, possibly even among independent voters. I think many people are skeptical of science, or like to buy into the under-science (such as science that tells us we are secretly being poisoned with Diet Coke or something like that). They don't see this as McCain being an anti-science idiot, but a brave free-thinker.
I also think this may be also be at the root of McCain's problem with conservatives, his recklessly self-righteous. This is a case where some caution is a good thing. He may have given a legitimacy boost to a movement that rightfully should be fading in the face of good science. All this from the experienced, elder statesman.