Here is a very interesting explanation of Trump's continuing popularity:

While all the other candidates are boxing, Trump is wrestling.
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In the current campaign, Trump is behaving like a professional wrestler while Trump’s opponents are conducting the race like a boxing match. As the rest of the field measures up their next jab, Trump decks them over the head with a metal chair.

You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.
R. Buckminster Fuller