So I'm kinda thinking that McCain is taking a dive. My theory: he really is a "maverick", and he was so outraged at the Rove wing of the GOP that he's made it his mission to dismantle the party from within. To do this, he's had to sublimate his natural charm and political instincts and beliefs and adopt this persona of crazy old wing nut crank.
In this context, his VP choice makes perfect sense. Why else would you pick a VP candidate that negates your best argument against your opponent while simultaneously alienating the very subgroup you've spent the last month targeting? He's setting the GOP up for an electoral disaster it'll take decades to recover from.
If he pulls this off, he deserves a statue. Destroying his own reputation, career and legacy for the betterment of the American people: that truly is heroism.