It's fashionable for the professional democrats (not the Professional Left) to blame Dem voters, a concept which, without evidence, quickly morphs into The Left, for not turning out for midterm elections. There has only been one midterm election in my memory which was actually about something, and that was in 2006. It wasn't about something because the professional democrats made it that way, it was because Iraq turned into an undeniable shitshow and the Dems almost didn't have a choice. Reality forced them, kicking and screaming, into running a national election. The midterms are usually a battle between one party which promises to kick the undeserved in the nuts, and another party which doesn't promise the nut kicking but doesn't promise anything else either. People like the idea of other people getting kicked in the nuts. That's not nice, but it's true.
That's the election strategy, coupled with forcing candidates to spend all of their time until Labor Day or so raising money, and then spending it all on TV ads. ZOMG we lost again! The Left didn't vote! Vote for what?
2016 is not a midterm election. but...