Well the maths in the Democratic race means that neither Obama nor Clinton can win on the basis of the remaining primaries and caucuses. Why? Well, according to the Washington Post:
"There are 3,253 pledged delegates, those doled out based on actual voting in primaries and caucuses. And you need 2,025 to win the nomination. To date, about 55% of those 3,253 delegates have been pledged in the voting process -- with Clinton and Obamb roughly splitting them at about 900 delegates a piece. That means there are now only about 1,400 delegates left up for grabs in the remaining states and territories voting.Hmm. So how is it going to work. Well, the superdelegates will get to decide things at the convention. Briefly, superdelegates are a mix of senior elected officials like senators, governors and past presidents and party hacks. There are about 800 in total and so far 300 have declared, favouring Hillary by about 2-1.
"So, do the math. If they both have about 900 pledged delegates so far, they need to win more than 1,100 of the remaining 1,400 delegates to win the nomination through actual voting.
"Ain't gonna happen, barring a stunning scandal or some new crazy revelation. So, they'll keep fighting this thing out, each accumulating their chunk of delegates, one of them holding a slight edge and bothing finishing the voting process with 1,600 or so delegates. And then the super delegates decide this thing. That's the math."
Superdelegates sit with their states in the convention but are not tied in any way as to how they vote. They can even change their mind at the last minute.
The theory goes that Clinton - being the party time-server - has the superdelegates in the bag. But equally, how would the party look if the wishes of the majority of elected delegates was ignored by the superdelegates. So Obama can still win, but he needs to beat Clinton as decisively as possible in the remaining contestsn and carry the momentum into the convention. He'll be battling as hard as possible for every delegate because he knows that if Clinton is leading going into the convention (or if Obama is only ahead by a few) then the superdelegates will find it easy to back the establishment candidate.
For more, there is a superb Youtube explanation from talking points memo