Sanders though has the "wow" factor for Republicans. They might turn out just so he doesn't get elected. Democrats upset with where Obama has taken the party (which is a rather large group) may be similarly motivated. The Republicans are stuck in a spot though where for Hillary, they need a strong conservative, but for Sanders they need a moderate. I think the VP choice later will prove interesting with that in mind. Also, one Sander's main support demographics, young people, has the lowest turnout rates. For presidential elections, a third of them would be pretty good. For midterms, 20% is rare. Even if twice as many turn out as usually, say even 70%, it still needs to be the right spread of that 70% to win the right states because of this nonsense system we have. The real kicker is many, even most, voters won't decide untill three weeks before the election anyways, so these next 14.25 months are utterly useless to boot.