I stand corrected.
Nevertheless, I do not think Trump is the "one trick pony" his detractors seem to believe. Whether by choreography or improvisation, he has defied expectations, and that under unprecedented opposition.
While I understand your and Krauthammer's thesis, without some galvanizing act I can't see anyone else catching him with a slow steady ground game.
His initial appeal may indeed be a nominal 20%, but success has its own appeal, and thinking in terms of an absolute cap seems a bit premature to me.
We are in the early innings so we are both entitled to our own guesses, er, analyses.