That is a great question. I do not know the answer. Either I vote for neither (basically don't vote) or I hold that the playing field is level and vote for what I think is most prudential. Since I think that governmental use of torture is just as grave as the government's permitting people to get an abortion, I must then either vote on the basis of other issues or not vote at all. I can't personally use the argument that there are many more abortions than there are cases of governmental torture because that would be consequentialist. So I do not know what to do.
I feel likewise, and I'm not sure what I'm going to do.
I cannot vote for either possible Democratic candidate, because both enthusiastically endorses the killing of innocent children in the womb. However, to the best of my knowledge the Republican candidate at least implicitly endorses the torture of human beings, which is also intrinsically immoral (I realize McCain says he's against it, but I'm pretty sure he voted for this bill - someone correct me if I'm wrong).
However, I think I must disagree with your appeal to consequentialism. In this case, we are not asking which one is morally permissible for you to do - perform an abortion of ten children or torture one person. In that case, neither are permissible. We are determining prudentially which candidate would do less evil - the candidate who supports the murder of millions of innocent children or the torture of a handful of suspected terrorists. Again, both abortion and torture are morally evil actions, but I personally am going to consider McCain as the lesser of two evils precisely because I think abortion the greater practical evil in the world today.
Of course, I may end up voting for some quixotic third-party candidate (which I've done before). I don't see that as throwing away my vote, as who says we are required to vote for one of the two major parties?