One virtue of having a reputation as a straight-talker is that you can get away with constant lying. For example, in response to a question about why he twice voted against a commission to investigate the response to Hurricane Katrina, John McCain says he voted in favor of every investigation. In reality, just as the New Orleans local news reporter said, he twice voted against a commission to investigate the matter.
Now there's probably some crazy strained reading of McCain's remarks so that his claims are consistent with reality. And since everyone knows McCain's a straight-talker, the press will read it that way. And because that's been the press's response each of the dozens of times in the course of this campaign that McCain's told bald-faced lies, his reputation for straight-talk never vanishes. A lesser figure who was in the habit of constantly lying and flip-flopping would develop a reputation as a kind of madmen, so invested in self-love that he thinks he has no obligation to political principles or basic factual accuracy.