Assuming they do, why this pick? Desperation? Extra media coverage? Apeasement of the Evangelicals or D all of the above.
The options suggest a bias before the fact. No sense of desperation currently as the race is generally seen to be a statistical dead heat at the moment. And you say "media coverage" like it's a bad thing

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Appeasement to more right/religious cohort may be a gain but it can't be a foundation of the choice. Governor Palin doesn't have an overt religiosity on her political resume' and that branch of the party just isn't the juggernaut that it used to be. Plus, you really think they're voting for Obama/Biden?
Just a guess but I think the biggest hint to the choice was in her speech the morning. The several mentions of "reform." Both what she'd done in Alaska (which was significant) and that they'd look to continue the same at the Federal level. Just a hunch, but I've thought that when Senator McCain closes his eyes and sees an image of himself he sees a guy in a Superman shirt but with a big R rather than a big S.
He pushed hard for his view of ethics and campaign reform. He thinks he sees a kindred spirit.
Sooner or later the campaign will have to respond to the Obama language that places him running against Bush more than McCain by simply saying "hey, remember, I ran against that guy too." That should effectively blunt the effort to co-locate any perception of Bush and McCain as siamese twins.
There are other issues with the Palin choice for sure. Those you mention I really don't see as vital among them though. If the McCain campaign is smart he'll even do a little tongue in cheek with the popularity she'll gain for awhile and be like Jack Kennedy was with Jackie when they toured Europe together during his Presidency. "Hi, I'm the guy accomanying future Vice President Palin around the country for awhile."
If she works well and doesn't shrink before the national press and they make a real issue of specific and large future reform they co-opt the "change" message from the other side and make some real gain because of the choice. They do limit the attack they can make on Obama's lack of experience with the Palin choice but the Obama campaign can't exploit her limited chops either. Doing so, after all, would only highlight his own limited record.