How does one respond to the Trump irrationality?

Given that Donald Trump's candidacy- and the widespread support for it- are both irrational phenomena fueled by a monumental ego on one hand and total irrationality on the other, how does one respond to those who have been taken in by The Donald?

Jim Geraghty hits the nail on the head.

As Mike Huckabee said the other day about the Iowa Caucuses, "He who is hot when the weather is hot is cold when the weather is cold." Trump's supporters will get better in time for February.