Democrats everywhere (including here) were focusing on the presidential race while the GOP has been quietly building a bench in local and state governments. It is why they have so many trifectas (I'll give them gerrymandering too). But you can't blame gerrymandering when the Republican is running unopposed. We need to run people for every office from school board to dog catcher to POTUS. In fact people on here should consider running themselves.
Another problem is that we (and the other side) increasingly live in a bubble. There's stories on here about how people cut off their Trump voting family members, block them on FB, etc. If we don't listen to the other side, we can't talk to them. I stayed off social media this election cycle and my sanity thanks me for it.
Bubble 2.0--- Democrats need to eliminate the following words/phrases from their vocabulary. Deplorables (IMO that comment was Hillary's 47% moment) and flyover country. President Obama won quite a few states in 'flyover country' that were later flipped by Trump. If Joe Voter in Iowa, Ohio, Wisconsin, or Michigan hears a California Democrat referring to his state as 'flyover country' he's probably turned off to the party. We won't win any voter this way.
It is 2017 now. We have two governor's races this year (NJ, VA), one is a surefire Democratic pickup (if we don't blow it) and the chance at a trifecta. We have the state houses in those states too (one in VA, both in NJ). In addition to the major races, we have local and county races to focus on. Join your local party and get involved with them. Donate your money or time to a candidate of your choice. Perhaps DU needs to have a 'candidate of the week' and highlight local races.