Not to defend the pollsters, but if they didn't get the pre-election surveys right, why would the get the post-election surveys right?
(Actually, I guess that's not exactly a defense of the pollsters' abilities at all, is it? Hee hee.)
I'm also a total believer in the average person's inability to remember how they felt on an issue one week in the past compared to today, much less a month ago or more. Lots of people rationalize outcomes in their own minds after the fact.
Maybe the variation is accounted for by the minority which didn't make up their minds early on. Maybe the people who said they made up their minds months ago were lieing.