SuperDelegate Math: Right now, the debate is over the manner in which the SuperDelegates should exercise their influence at the Convention this summer, ie., should they vote for the candidate who leads in pledged delegates, should they exercise independent judgment, or should they reflect the will of their constituents. Obviously, if you support Obama, you're more inclined to freeze the race after the last primary, since he will probably be ahead in the pledged delegate count, and/or the combined popular vote, after all the votes are counted.

But if every SuperDelegate were bound to vote for the candidate who won his state's primary or caucus, as of today Clinton would have a narrow lead over Obama, 230-224, even though she trails in the combined popular vote by almost a million.* This reflects the fact that Clinton's wins have generally been in large Blue states, which have a disproportionately higher number of SuperDelegates, and have been by relatively narrower margins, while Obama's wins are generally coming from states that vote Republican, and thus have fewer delegates. I suspect that if SuperDelegate votes were determined by who won a Congressional District, or by even smaller, localized criteria, Obama would have the lead.

All the more reason why the contests in Ohio, Texas, North Carolina and Pennsylvania will decide this battle well before the Convention. Most of the SuperDelegates are going to have more loyalty to their local constituents than to some amorphous determination of the national will that could be established by a series of contests over a six-month period. Many of them are elected officials in their own right, and have more concern with their next election than they have in supporting whichever candidate wins a narrow plurality in the rest of the country. A Clinton sweep of the remaining four largest states would give her the clear momentum heading into Denver, and give her a stronger electability argument over the slumping Obama, while an Obama win in any of those four states would thwart that narrative.
*I have not counted SuperDelegates from Florida or Michigan in this total.