If the Democrats continue along the current trend of never ending investigations despite the results of the Mueller report and also have candidates that continue to want to change the Constitution and lean way to the Socialist side of things, they will be handing the next presidential election to the incumbent.
The Democrats will have no one to blame but themselves although they won't see it that way. You think the obstructionism is bad now? It will pale in comparison to what will happen when Trump is reelected. Demonstrations, riots, destruction, protests inside and outside of Congress and other boorish behavior, the likes we haven't seen since the 60's.
That's the way to win people to your side of things.