Chuck Todd on MSNBC just advanced one hypothesis for why Hillary seems to be doing so much better than expected. One theory: Obama was so far ahead in the recent tracking polls that many of his supporters assumed he'd win easily and didn't show up to vote. Which reminds me, of course, of the Simpsons episode in which Bart loses his race for class president to Martin Prince by a count of two votes to none because, despite overwhelming support for Bart, none of his supporters bothered to cast ballots.
Let the speculation begin as to whether the Clinton camp's whispering about an Obama blowout was serious analysis or shrewd expectations-setting. I'd be inclined to believe the latter if not for the fact that everyone else seemed to be saying the same thing.
Update: Clearly I originally gave this post the wrong title--it's Hillary, not Obama, who holds the position analogous to Martin Prince's.