In this article by ABC News' Jake Tapper, he reports that Ariana Huffington claims John McCain told her in 2000 that he did not vote for George W. Bush. Given Huffington's left wing credentials, one supposes her intent is to hurt McCain with Republican voters. It won't work. Republican voters will hold their collective noses and vote for McCain anyway, as the clear lesser of two evils.
What Huffington has inadvertently done is helped McCain with independent voters. By increasing the perceived distance between him and our unpopular President, she has made McCain more attractive to folks who, for whatever reason, don't want to vote for whichever damaged Democrat ends up with the nomination.
Moral: Unintended consequences are everywhere.