(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.
What happened to Republican moderates?
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.