There no way Trump wins in 2016 if he was going against somebody that was actually popular.

No way he would have won the primary without Hilary’s Pied-Piper Strategy

This isn’t even entirely an optics problem. Democrats in leadership believe they are best served when they are the centrist running against fascism rather than a progressive running against some boilerplate business conservative. So they actively encourage the freaks in the GOP while fighting tooth and nail to keep greens and socialists off their end of the ballot