Randy Alcorn has an excellent post up today addressing what our votes really represent, and the issues related to not caring for either candidate.
In fact, the linked article contains links to Randy's previous posts on election matters, all of which are thoughtful, insightful, Biblically grounded and gentle in manner, like all of his other writing.
In particular, this post discusses the "lesser of two evils" question, and the people who throw away their vote (my words, not Alcorn's) by casting it for a candidate from a third or independent party who has no hope at all of winning election. The problem for some Christians, however, is that in voting for what they may view as the "lesser of two evils", they are still voting for, therefore condoning in some way, "evil".
In the end, however, we need to remember that this world is a temporary place. Alcorn sums it up well:
Because you know this world is not your home, and that it is terribly fallen, you put your hope in Christ, not in this country. But as a steward of your American citizenship, you try your best to support good and resist evil, realizing how that is best done in politics isn’t spelled out in Scripture, and godly people will see it differently. Then, together with those who agree on Christ who is primary and disagree on what’s secondary, you trust God and serve him and hold up Jesus Christ and the gospel of grace as the only hope for this nation and this world.