Here's why Obama's apparent Missouri win is such a big deal, if it holds: It goes a long way toward over-turning the exit-poll engineered expectations Obama was failing to live up to as of about ten minutes ago. I suspect the same pundits who (completely preposterously) concluded that the bottom had fallen out for Obama after Massachusetts, New Jersey, and (what they thought was the result in) Missouri will now find themselves lunging back in the other direction.
Of course, they'll be wrong this time, too. The reality is that tonight's results are basically a draw. (Though I think a draw favors Obama, for reasons I explained here.) But it goes to show how ludicrous the media's approach to this stuff is.