Today's Washington Post reports that Sarah Palin's attacks on the media have spilled into what the columnist Dana Millbank politely calls "ugliness." At a rally in Clearwater, Fla., after Palin aroused the crowd with attacks on Katie Couric, Palin supporters "turned on reporters in the press area, waving thunder sticks and shouting abuse. Others hurled obscenities at a camera crew. One Palin supporter shouted a racial epithet at an African-American sound man for a network and told him, 'Sit down, boy.'" At that same rally, a Palin supporter yelled "kill him" after Palin worked the crowd up with her accusations that Sen. Barack Obama "pals around" with terrorists.

This is not just ugliness. It is demagoguery, and it is dangerous.

Think about this for a moment. Can any of us imagine the horrified outcry if Barack Obama had worked up a crowd of African-American supporters with verbal attacks on whites, and then the crowd had turned on white reporters, waving sticks, shouting racial epithets, encouraging others to assassinate a political figure?

Populism has a long and venerable tradition in American history, but populism can quickly turn into demagoguery. When populists encourage not just a resentment of elitism, but a contempt for elites; when populists express not just distrust of the media, but encourage hatred of a free press; when populists inspire not just emotion, but demonize the "other" to incite a crowd to violence - these are all signs that a leader is crossing the line between populism and demagoguery.

Sarah Palin crossed that line at her rally in Clearwater, Fla.