A look at John McCain's primary run from The Daily Beast:

The decent thing for McCain to have done after Obama’s election would have been to say that he was calling it quits, giving way in the Senate to a politician less spent. But he didn’t. Politicians without a guiding ideology are, frequently, the ones who stay in the game longest. Manic redefinition, constant reorientation, tracking the latest directions on the ideological GPS, places them on an unending trajectory of reelection, a journey that ends only with death. The late Senator Robert Byrd was one such man; McCain, without Byrd’s godawful stains, is shaping to be another. I don’t have reliable data on the topic, so consider this an anecdotal observation, but this is how vainglorious politicians often end their careers—hanging on a little too long, at great cost to their public image. Think of McCain as the Liza Minnelli of American politics.