This is a typical analysis of the polls and the election outcome. It’s credible, but besides the point.
Democratic voters didn’t turn out because they didn’t have a reason to. Same thing with independent voters – they weren’t given a reason to break Democratic. Back in 08 and 12, they had “hope”, but in 2014 they still hadn’t seen any “change”.
In part, there has been change, but the Democrats didn’t run on their record. It would have meant they had to change minds with arguments and information instead of relying on previous strategies of “targeting”. Passive versus active.
In part, there hasn’t been change, because Obama is naturally cautious. This is probably a good thing overall – if you’re Jackie Robinson you are very, very careful. However, the Democrats needed to throw their coalition some “red meat”, particularly on immigration. Obama should have acted on immigration before the election. That would have brought out the Latino vote.
As it was, their reaction was either “why bother” or “let’s see what the Republicans can do”.