George Monbiot writes in the Guardian: How these gibbering numbskulls came to dominate Washington
Some choice quotes:
Perhaps the defining moment in the collapse of intelligent politics was Ronald Reagan's response to Jimmy Carter during the 1980 presidential debate. Carter - stumbling a little, using long words - carefully enumerated the benefits of national health insurance. Reagan smiled and said: "There you go again." His own health programme would have appalled most Americans, had he explained it as carefully as Carter had done...
One theme is both familiar and clear: religion - in particular fundamentalist religion - makes you stupid. The US is the only rich country in which Christian fundamentalism is vast and growing.
On the media:
... perhaps the most potent reason intellectuals struggle in elections is that intellectualism has been equated with subversion. The brief flirtation of some thinkers with communism a long time ago has been used to create an impression in the public mind that all intellectuals are communists. Almost every day men such as Rush Limbaugh and Bill O'Reilly rage against the "liberal elites" destroying America.