Two devil's advocate questions:
What is the difference between (1) granting that there is no perfect candidate, and (2) voting for the lesser of two evils?
If a candidate is not perfect and you vote for him, are you not voting for evil?
When one asserts that he will not vote for the lesser of two evils, he may get kudos for his ideological purity. But the burden of proof remains on him to explain why he could not vote for that "imperfect" candidate. On the other side, the more mainstream voter cannot simply appeal to the "no perfect candidate" slogan. He needs to explain why his candidate's positions are not evil, just not ideal.
Christians draw this line in different places, and then judge others harshly for not drawing it where they do. Very sad.