Marc Ambinder on the uncommitted Democratic superdelegates:

So if Rep. James Clyburn (D-SC), who comes close to calling former President Clinton a racist, who believes that African Americans think that the Clintons “are committed to doing everything they possibly can to damage Obama to a point that he could never win,” who says these things in multiple venues (Reuters, the New York Times).... still won’t endorse and still won’t call for Clinton to drop out, should it surprise us that other superdelegates are even more shy?

Personally my suspicion is that a large part of the non-commitment by the superdelegates is that it goes against the way politicians deal with the tough issues—in large packs like roll-call votes where they can be at least somewhat anonymous. There is no “safe vote” now—or at least there’s nothing that is obviously the safe vote—so why commit now when in a few weeks you might have the political cover to commit after the heat is over?