Vox gets it right.

If you call yourself a conservative and you vote for McCain, you should be aware of two things. First, you are not a conservative. Second, you are an idiot. As I wrote on Monday, only a vote for McCain is a wasted vote because it's the only vote that will not provide you what you think you're going to get. The left-liberal votes for Obama and knows he'll get socialism and multi-culturalism in one way or another. (The pacifist, on the other hand, will be disappointed.) The third-party voter votes third party and knows he'll get nothing. The non-voter doesn't vote and doesn't get what he isn't expecting.

The Republican voter, on the other hand, usually votes for conservatism, constitutional judges and small government, but only gets liberalism, activist judges and big government. That's why it is the Republican vote that is truly the wasted one.

Vox Day

Added emphasis is mine.