Matt Stoller has a useful reminder to people (like me) touting the power of McCain's war-hero biography: "1992, 1996, 2000, and 2004 all saw the candidate without military service elected over the candidate who had served, in several cases heroically."
Update: Ed Kilgore has more thoughts on this:
McCain may be in the process of making the same big mistake his friend Kerry made in 2004--making his biography the overriding centerpiece of his national security message. Sure, McCain's war record attests to his character and patriotism, but hardly means he'd be an effective commander-in-chief. If that were the case, we'd only have military leaders as presidents. What McCain has to say about national security issues will, over time, have as great an impact on how he's perceived by persuadable voters as endless clips of him in uniform or returning from the Hanoi Hilton. The tragedy of the Kerry campaiign was that the man did have a pretty powerful grasp of national security challenges and what to do about them, but it never much got a hearing thanks to the back-and-forth about his own "story."