What date is the first primary? Iowa, I guess.
My guess is that Governor Palin will declare just a few weeks before the Iowa caucus. (Unless there are some rules that makes it obligatory to sign up months ahead.)
The day after the presidential election she said on local radio in Alaska that if she would run, she would have to run a completely unconventional campaign. I think it may still be on the cards.
The US (and the world) could do much, much worse than President Palin. (In fact we already have!)
And, you'd expect to have a chance in Iowa if she did that?