John McCain may be a dick. He may be an entire bag of dicks. He may even be a giant, dick-shaped bag full of dicks. But it's not because of his choice for Vice President.
What are the major problems that McCain has with his campaign? Some people think that he's too old (he turns 72 today). The conservative base of the Republican party was upset that he won the nomination, and continued to seek assurances that he wouldn't abandon them. And despite fashioning himself as a 'maverick', Democrats continue to paint him as a Washington insider and a continuation of the failed policies of George W. Bush.
Sarah Palin shores up all of these weaknesses. She's young, she's a Washington outsider, and she's a hardline conservative. Her gender certainly wasn't something that they ignored when they vetted her as a candidate, but it's a lot deeper than that. She's no Geraldine Ferraro.
And before anyone dismisses this as electioneering on the part of the GOP, take a look at why Barack Obama selected Joe Biden as his running mate. The main talking points against Obama were that he wasn't ready to lead and that he had no experience with foreign policy. Well, that's precisely what Biden brings to the table. They've both selected the candidate that they feel gives them the best chance at the White House.