The Democratic party indeed got entrapped by its fringe but the same thing happened to the Republican party. It's the result of the system incentives that favour such polarization.

I think what's going on is that trump supporters don't quite take him literally on the details of what he says.

Now, as to whether Trump will or won't do more damage in this term, that really depends on whether this time the people around him will stop him or whether he will choose people who will be more loyal.