Apathy always crushes Democrats. It's why they lose off-year elections. It's why Republicans have a stranglehold over local governments (and the redistricting power that comes with it). They'll come out to vote for Hillary (or against Trump), but then everything will go back to the Republicans two years later because they can't be bothered to come out and vote.
So far it looks like the choice is between Hillary Clinton and Donald Trump. I like some of what Sanders stands for in the abstract but as a candidate I don't find him terribly compelling for multiple reasons. There's just nobody I can get fired up about. There's nobody I actively really want to be president. Can we just leave the office vacant?