I doubt half of what politicians say say they believe is what they actually believe. Dr. Carson (and much of the Republican candidates) stand to benefit by professing a belief in creationism. Liberal politicians do it just as much.
Personally I want a physician who is competent and cares about my well-being. I don't see how Dr. Carson believing in evolution vs creationism changes that. I don't know anything about him personally though, so if he were a "militant believer" one way or the other, that would make me question his ability to be open-minded and his tolerance for ideas different than what he's used to.
Like many out there, I don't see how evolution threatens the existence of God. The Catholic Church supports evolution (not necessarily all Catholics do, but the official Church standing is evolution explains our physical existence and God explains our spiritual existence)