What happened to Republican moderates?

WARREN, MI - MARCH 04:  Republican presidential candidate Donald Trump speaks to guests during a rally at Macomb Community College on March 4, 2016 in Warren, Michigan. Voters in Michigan will go to the polls March 8 for the State's primary.  (Photo by Scott Olson/Getty Images)

(CNN)Here is a much simpler explanation for Donald Trump: Republicans have fed the country ideas about decline, betrayal and treason. They have encouraged the forces of anti-intellectualism, obstructionism and populism. They have flirted with bigotry and racism. Trump merely chose to unashamedly embrace all of it, saying plainly what they were hinting at for years. In doing so, he hit a jackpot.

The problem is not that Republican leaders should have begun to condemn Trump last year. It is that they should have condemned the ideas and tactics that led to his rise when they began to flourish 20 years ago.