The last time a Democrat sat in the White House, he faced a nonstop witch hunt by his political opponents. Prominent figures on the right accused Bill and Hillary Clinton of everything from drug smuggling to murder. And once Republicans took control of Congress, they subjected the Clinton administration to unrelenting harassment  at one point taking 140 hours of sworn testimony over accusations that the White House had misused its Christmas card list.

Now it’s happening again  except that this time it’s even worse. Let’s turn the floor over to Rush Limbaugh: “Imam Hussein Obama,” he recently declared, is “probably the best anti-American president we’ve ever had.”

To get a sense of how much it matters when people like Mr. Limbaugh talk like this, bear in mind that he’s an utterly mainstream figure within the Republican Party; bear in mind, too, that unless something changes the political dynamics, Republicans will soon control at least one house of Congress. This is going to be very, very ugly.

So where is this rage coming from? Why is it flourishing? What will it do to America?

Anyone who remembered the 1990s could have predicted something like the current political craziness. What we learned from the Clinton years is that a significant number of Americans just don’t consider government by liberals  even very moderate liberals  legitimate. Mr. Obama’s election would have enraged those people even if he were white. Of course, the fact that he isn’t, and has an alien-sounding name, adds to the rage.