Strategic Credibility

Here's how I think McCain gains his credibility. He publically arranges to do something substantially different from the party line, or makes some statement critical about a policy, and then makes sure the media covers it as if he's what he says he is.

The rest of the time, he does the standard things. The trick is to have those moderate, bipartisan things (or things that seem that way) be the face of his political career, rather than the stuff he actually does.

The key is to get the maverick, bipartisan, moderate stuff out in front, so when he backslides in private, he still appears like he's got the potential to do something surprising.