Let's look at the 2010 mid-term polls as a predictor for 2018
I was looking at some polling data as the 2010 mid-terms approached. You know the year. That's when Democrats lost 63 seats in the House.
As the generic ballot margin gets slimmer for the Democrats, Republicans feel as though the doom that's predicted may really not be inevitable.
In September of 2010, the Dems held a slim, one point lead in the generic ballot (it actually was a Rep.+2 advantage on election day). But, the Republicans held a 19 point advantage on enthusiasm.
As it turns out, the lead in the generic ballot may be nice, but it is far less important than the enthusiasm gap, and right now, the Dems hold a larger lead in that category than the GOP did in 2010.
Link to 2010 Gallup poll:
http://news.gallup.com/poll/143132/generic-ballot-virtually-tied-democrats-republicans.aspx
"Enthusiasm" is usually a gauge of hard work, communication, networking and convincing. So, before you start posting "the polls don't matter, we just need to work and get the vote out" I get that part. In fact, part of my salaried position is getting pro-union, Democratic votes out, educating voters and convincing union members why the Democratic Party is our best bet. Let me tell you something you may already know, that's a full time job, especially in the trade unions. Mostly white, mostly male, mostly without a college degree, mostly over 35 (and many over 50) is not quite the Democratic demographic. So, you can rest assured, I get it.
These figures are important because I believe we'll win, and win big in this off year election. We just have to keep that "enthusiasm" up.