A maverick would not pick a VP based on pure political expediency. A strong argument can be made that McCain's pick is the among the most politically pandering VP pick, ever.
His biggest decision to date was to pick someone who could/should be president and for the life of me it's hard to imagine this is the best choice, or even in the top 10. Hell, if he wanted a woman, what about Kay Bailey Hutcheson?
The most disturbing fact is that McCain met her once in February 2008. Once. How can you make the most important decision to date after meeting someone one time? Does he really know Palin? Doubtful. That alone should send shivers down even the most ardent McCain backer.