He picked a VP which is nothing but a purely political choice.
Palin has been a governor for a short time and a mayor before that. She has no federal experience, no foreign policy experience, and exemplifies every single one of the staunch conservative values (anti-abortion, anti-Science, pro-drilling, pro-2nd amendment). Frankly, her selection as VP running-mate is a disaster... perhaps not for McCain, as Americans don't tend to vote based on the abilities of their leaders so much as their promises, but certainly if the Republicans do get another Presidential term this woman has the potential to do even more damage to the USA's international reputation.
She's a terrible choice in all practical terms, and I sincerely hope this obviously political move doesn't pay off in the slightest.
There are far more qualified and far better balanced women he could have chosen. Frankly I'm somewhat surprised at a choice this poor.