Can one morally vote for the lesser of two evils? In a word, no. A basic principle of Judeo-Christian teaching and of the natural law to which the country was married by the Declaration of Independence is that one may not knowingly do evil that good may come of it.
So, is a vote for [a third party] or no vote at all wasted? I reject the idea that a principled vote is wasted. Your vote is yours, and so long as your vote is consistent with your conscience, it is impossible to waste your vote. – Judge Napolitano