I believe that Bernie Sanders is going to win the Democratic presidential nomination because Hillary's world is falling down around her. She is going to end up in jail for all of the things she's hidden and done. Sanders is also getting a lot of followers with his 'free stuff' views. A lot of college student's seem to be on his side since he's promising free college.
While it does not currently appear as if Sanders will win, I believe it is fully possible that he can overtake Clinton in the delegates race. There are critical states that Sanders trends strongly in that have not yet conducted Primaries, so it feels like it's way too soon to discount him.
All the power of the Democratic Party establishment is presently positioned to aid Hillary Clinton in her nomination bid. In the Democratic process, superdelegates play a prominent role. These superdelegates are not bound by the results of state primaries and caucuses. At the current time, these superdelegates are overwhelming supporting Hillary since they are generally connected to the party establishment. Sanders will not be able to overcome the weight of the superdelegate count to win the nomination.
While many people want Bernie to win the nomination, Hillary to date has received a greater percentage of the support among the American people and have more delegates to show for it. While it is possible for Bernie to come back, being behind at this point puts him at a significant disadvantage.