Ezra Klein gets it:

I wouldn’t read too much into this as a tactical victory: Palin has collapsed for fairly predictable reasons: It really is the case that she’s grossly inexperienced and unsuited to this moment. If she had to sit down for a 30-minute interview on the financial crisis, there’s no one who doubts it would be a catastrophe. Democrats highlighted that fact, but it’s not as if it was a brilliant attack they made up. If Palin continues to bottom out, it will, more than anything, suggest that sometimes, even in politics, the reality of a situation eventually overwhelms the spin.

It remains to be seen, of course, whether the enthusiasm for Palin among the GOP base is enough to put her and McCain over the top – but at present, it looks like her doubters were more on the mark than those of us who thought her early momentum had the potential to be decisive. My own take on the likely causes of her collapsing favorability gap is here.