It's the superdelegates, stupid
ABC News' current delegate estimate has Obama at 1,555.
That means he would need to win 77% of all the remaining pledged delegates to hit the magic number of 2,024 to secure the nomination. That is highly unlikely due to the proportional delegate allocation rules in the Democratic Party.
Clinton would need to win 94% of all the remaining pledged delegates to hit the magic number of 2,024. (ABC News currently has her at 1449.)
So, clearly they both are going to be relying on superdelegates to secure the nomination.
Another possibility is that they have a "do-over" to reinstate the delegates of Michigan and Florida. In which case we're once again putting our faith in the completely bankrupt Florida election system. Michigan is the new New Hampshire.