The response from the Left is helping, if anything. Yes, she is inexperienced, but the Republicans obviously realised that that wasn't working as a charge against Obama, and decided to roll with it; and Obama's supporters now cannot really use Palin's inexperience against her without inviting the obvious counterattack - so what if Palin has only run a very small town and a very small state; that is still more than Obama has ever run (or, for that matter, McCain).
The news about her daughter is also a complete winner, in my view. Before it broke, rosefox had posted a very wise piece about how feminists should and shouldn't react to Palin's candidacy. The absurd and offensive Daily Kos story about Palin's own most recent pregnancy was a complete gift to Republicans, and they were absolutely right to mention it in the press spin about Bristol Palin, because it makes Democrats look really stupid. Obama's own response - that this is a private family matter, and anyway he was born to a teenage mother himself - is the only sensible one to make. It is tempting - and I've seen a lot of people succumbing to the temptation, in the blogosphere at least - to use the issue to highlight the weaknesses of the pro-life, abstinence education argument in general. I hope the Democrats on the campaign trail do not use this rhetoric; all it does is reinforce the impression of the Palins as a normal family to whom ordinary crises happen, and who then have to balance their own deeply-held beliefs against the needs of the moment. (And in any case, what influence would a Vice-President actually have on these policies? Probably less, in practice, than the Governor of Alaska.)
There are good reasons to attack Palin's judgement - her definition of clean government seems flexible enough to allow her to pursue family vendettas from the Governor's office. There are plenty of good reasons to worry about the McCain-Palin ticket; in my own area of particular interest, foreign policy, I confess I don't have a terribly clear image of what Obama's line actually is, but I have a good understanding of McCain's line - and it frightens me - and I know and respect a lot of Obama's people, which reassures me. So let's stay with the sensible stuff, OK?