My fear all along. I'd had to see the US democracy sacrificed on a cross of "progressive-ism," which I can see happening...I think we are about to test this guy's theory in the 2020 presidential.
I think there is a good bit of the middle that will not, cannot hold their noses and vote for Trump. His behavior is just not acceptable.
If the Democrats nominate a sane person, they could well pick up a lot of those voters.
If, on the other hand, they nominate an extremist, they may fire up their base, but they stand to lose convince-able middle of the road voters.