Anecdotal bit about today's poll failure
I remember listening to the NPR commentary leading up to the Iowa caucuses. The Iowans tended to say who their candidates were, or who they were leaning toward, if they were undecided. Then while listening to the New Hampshire coverage this morning, with voter-on-the-street interviews at polling places, the voters would clam up. Sure, some said which candidates they liked, but it was more common to hear them say things like, "I know who my candidate is," or "Oh, I'm deciding between two right now."
For whatever reason, New Hampshire voters seem to prefer to keep such information to themselves, at least on these programs. Maybe I'm reading too much into it, but that does seem like at least a partial explanation of what could have happened.
All those irregular primary voters probably threw off polling, too. I'd imagine polling works better if you've got a more predictable sample to work with. Regular voters are predictable, but the kind that don't usually bother are probably more difficult to figure out.