To my earlier response I would add this; Trump didnt win the election, Hillary lost it. He wont be running against Hillary in 2020, which means no emails or birth certificates or Benghazi to campaign against. The Democrats were cocky and complacent and full of hubris in the last election; you can be sure they will not make that mistake next time.
I would agree - she lost it, but others were complicit too - Obama's extreme left policies, the DNC scandals that included cheating, lying, email BS, campaign leaders that did some really stupid crap - all of that led to her demise. With that in mind though, people took this election as a chance to tell the left that the line has been crossed and even moderate Dems think things have gone too far left (such as folks in my family). Problem for the Dems is that the DNC leadership, instead of learning from that, are doubling-down on the stupid, looking to run in 2020 on men in girl's bathrooms, gun control and protecting their Islamic friends over everyone else.
No, unless the Dems do a very substantial turnaround, I don't know that they'll be ready to take a victory in 2020, even against an easy mark like Trump. If they want it, they'll need a big name that moves more to the center, if they stay far left, I have a feeling the Dem voters won't turn out for them again. Time will tell.