I think John McCain made a clever short-term political move in selecting Mrs. Palin for the VP nomination. First, she's a woman and a mother, and by virtue of that alone he might shave some of the bitter Clintonites or radical feminists off of Barack's support. Second, she's a "reformer," and one of the most popular politicians in the country, at least with her constituency. Third, she's a hard-core social conservative, which will no doubt please the far-right base whose support McCain has been trying to solidify. She's a major fan of both the NRA and the pro-life agenda, which will help McCain in backwoods-y communities across this great nation. Fourth, she's young and new and not terribly wealthy (drives a Jetta to work every day) and so she can serve as a rebuttal to the "McCain is old, rich, and therefore out-of-touch" line of attack. Fifth, she is a big proponent of domestic drilling, going even further than McCain to support opening ANWR. This will bring in the campaign cash from the Republicans' buddies in the oil/gas industries, and will reinforce the Republican "drill here, drill now" mantra. Finally, the pick definitely caught the Obama team off-guard. They were, like everyone else, preparing to attack a McCain-Romney ticket, so McCain definitely has the advantage of surprise here, for what that's worth.
Upon closer inspection, however, there are some important disadvantages that the Democrats can certainly exploit. First, there's the issue of her readiness to be POTUS in the (more-likely-than-usual) occurrence of McCain's death or major physical/mental deterioration. This woman has only been in politics (beyond the level of a city council in bumfuck, Alaska) for ten years. Her current term as governor is her first, and its in a state that doesn't exactly represent the heartland of America in terms of population, issues, or values. Her political experience is next-to-nothing and I think the case can be effectively made that she is a very unknown quantity for someone who very well might have to step into the presidency. This should be the Democrats' #1 objection to Sarah Palin, because it is the #1 risk that she presents to the country at large.
Second, and by virtue of the first argument, this VP choice shreds any Republican claim that Barack is too inexperienced or young or unproven in any way. Compared to Sarah Palin, Barack is a wizened political veteran. As this line of attack was one of the Republicans' most credible and fruitful, they've sacrificed a big offensive threat in order to have her on the ticket.
Third, the republicans will obviously be using Palin to encourage the idea that they can provide reform and change in Washington as well as the Democrats can. To me, and hopefully to anyone who knows even a little bit about American democracy, the idea that the Vice President is going to change ANYTHING about ANYTHING in Washington is bogus on its face. The VP doesn't do shit. He/she can provide useful advice and counsel, but the overall number one purpose for that office is to provide a well-known, elected official to take office if the president dies. That's it. Any rhetoric Republicans spout during the convention about Sarah Palin fighting government corruption and special interests in Washington is pathetically and clearly false. I'm just hoping that the Democrats can get that message out clearly enough and to enough people to counteract the inevitable "Maverick+other woman Maverick" propaganda that the Republicans will begin spewing.
Third, I don't want to short-change Mrs. Palin, but I think she's going to have her hands full, to say the least, when it comes to the televised VP debate against Joe Biden. This man has the political experience and oratorical thunder to truly embarrass her on national television, especially since she probably is not that well-versed in all of the policy issues facing America at large. I'm hesitant to put out a prediction without seeing her speak, but I think it's safe to say that she would do well to even hold her own in that debate.
Finally, it's also obvious, as I noted above, that Republicans will set her up to counter the "old/rich/out-of-touch" label that Obama's campaign has been nailing them with recently. Again, I think adding a VP who is not so old or rich (but is probably just as out-of-touch, if only due to lack of experience at the federal level) is not going to be an effective counter. It's not like a vote for Republicans is a vote for Sarah Palin's policies here. She's on McCain's ticket, not the other way around, and so she'll basically just be a fresh face in support of the same old policies. I like that she has shown a willingness to fight corruption and government waste, but if that's her true merit, she could do a lot more in Congress than in the Vice President's mansion.
To conclude, I think this is a smart political play in the short term for McCain, but I really don't think it will generate the advantages that the Republicans were obviously seeking over the course of the election. It could affect the female vote in a significant way, but it also robs the republicans of attacks they could make on Barack's (in)experience and youth. If McCain had set himself up as a statesman-like sage, with a ticket full of experience and credentials and accomplishments, he might have a good case for peeling away moderates and conservative Dems. By choosing a young, unproven, largely unknown VP, I think he ultimately made another mistake that will come back to bite him before November.