A lot of smart commentators seem to have written Sarah Palin off as a serious Presidential candidate in 2012 or beyond (she's only in her forties, so there are probably four or five more cycles where she could credibly run).  One of the more common justifications is that she's lost independents, and is upside down in her overall approval ratings.

I sometimes feel like I'm the only one in the country without strong feelings about Palin, and I certainly see a number of weaknesses in any Palin candidacy.  But I'm not sure that I would write her off because of her polling numbers.

Witness the polling numbers of another female politician who engendered strong feelings among members of the other party and independents. 

The polling numbers on Palin vary by question, but she's generally hovering at around 40% favorable/50% unfavorable.  These aren't great numbers for any politician.  But then-Senator Clinton was similarly upside-down at several points in the past decade, and although Polling Report doesn't have numbers going back to the beginning of the Clinton Presidency, I recall her being quite a bit less popular than Bill was (and he wasn't very popular from 1993 through 1995).  But she has also seen her approval ratings soar into the 60s, and had she spent some time and energy organizing her forces in caucus states, she'd probably be President right now.

Palin's weaknesses are certainly different than Clinton's were, but she has several strengths that Clinton does not.  I don't even know if she wants to be President, but if she plays her hand well over the next year or two and manages her "rehabilitation tour" well, she'll be in the running.