Jonathan links to Sen. Brownback's explanation of his views, which do indeed seem to reject the proposition that man evolved through a natural process from lower life forms. Nor, as best I can tell, does he take the view that evolution took place but that the mechanism for evolution was set up by God. Perhaps I'm wrong on this -- his argument isn't crystal clear -- but it seems that he is viewing man as a product of separate creation:
While no stone should be left unturned in seeking to discover the nature of man's origins, we can say with conviction that we know with certainty at least part of the outcome. Man was not an accident and reflects an image and likeness unique in the created order. Those aspects of evolutionary theory compatible with this truth are a welcome addition to human knowledge. Aspects of these theories that undermine this truth, however, should be firmly rejected as an atheistic theology posing as science.
How should this affect a person's judgment about whether he supports Sen. Brownback? I'm not sure I know the answer, but I thought I'd raise the question, and mention a few thoughts of my own. (Note that I am by no means a supporter of Brownback's, though I have no implacable hostility to him, either.)
1. We might argue that this shows Brownback believes things that are provably false, and that this reflects badly on his judgment. But while I myself believe in evolution, I can hardly say that divine creation is provably false, at least under any familiar standard of "proof." If God exists, and he can work miracles, he might have created man in a way that makes evolution look plausible. I don't see any evidence for this proposition, but I can't say I can disprove it. For that matter, I can't say that a theory that man was created by super-intelligent aliens -- either created from scratch or "uplifted," to borrow David Brin's science fiction term, from apes -- is provably false.
2. We might argue that this shows Brownback believes things about the physical world that are not based chiefly on reason and evidence, and that this reflects badly on his judgment. This is a classic burden-is-on-believers-to-show-it argument against belief in God: As a friend of mine put it, there is the same evidence for the existence of God (at least once evolution is available to explain the development of complex systems) as for the existence of werewolves. Yet we would comfortably say that "werewolves don't exist," and look askance at someone who says "wait, maybe they do exist, you can't prove that they don't." We usually put the burden on people who are claiming the existence of things to provide some evidence that they exist; a contrary view is seen by us as superstitious or unscientific (again, consider claims about werewolves, vampires, or ghosts).
Likewise, the argument would go, we should fault those who assume the existence of a God, and a miracle-working God at that, without real evidence or logical deduction. Of course, this assumes that we've rejected the logical arguments for the existence of God, but I've never found any of those to be particularly persuasive, and in my experience even many religious people don't rely on those arguments.
Note, though, that this argument would equally apply to candidates who sincerely believe in the Virgin Birth, in the Resurrection, in the parting of the Red Sea, and in any other miracle. Perhaps it should apply to them; but I do want to flag that this argument isn't peculiar to evolution.
3. We might argue that this shows Brownback, if elected President, will have a lousy science policy.
Evolution is not in some abstract sense the "simplest" or "most plausible" theory of the development of mankind or of other species. Divine creation is in some ways simpler, and to some more plausible. Evolution is the simplest or most plausible theory that doesn't require the existence of some external intelligence (whether God or aliens); in that respect, there is some truth to the argument that belief in evolution rests on a sort of judgment about the relevance of God just as creationism does.
But what makes evolution better is that this naturalistic assumption is much more productive of potentially useful predictions about the world. Compare, by analogy, the theories that the planets appear to move around the sky because of gravity, that the planets appear to move around the sky because divine beings push them, and that the planets appear to move around the sky because all reality is just a dream. The good thing about the gravity theory isn't that it's provably true and the others are provably false; they definitionally resist disproof. Rather, the gravity theory is the most useful theory -- most useful at predicting the location of planets, at developing machines, and more -- and the other theories aren't useful at all.
If this is right, then rejecting the theory of evolution would lead a Brownback Administration to misinvest science research resources, and to underinvest in research that assumes the theory of evolution. This might distinguish most beliefs about one-off miracles in the past; it's unlikely, for instance, that a government leader's belief in the Virgin Birth would lead to poor governmental judgments about funding of gynecology and obstetrics.
4. We might argue that electing Brownback would make America look foolish to world elites that accept the theory of evolution. On the other hand, note that this, too, is potentially true of electing people with various other religious beliefs; and query more generally how much we should guide our judgment by such concerns.
In any case, these are just some tentative thoughts. I offer them not because I'm sure about them, or because I feel I've settled on an answer, but just because I think this is an important intellectual and practical question, and I wanted to stoke the conversation a little.