Ezra Klein is a columnist at the Washington Post, as well as a contributor to MSNBC

The season premiere of “Mad Men” ended with Don Draper staring at the front page of the New York Times from Jan. 1, 1968. “World Bids Adieu to a Violent Year,” reads the headline. (The Times story, by Murray Schumach, is real; you can read it here.)

As in “Mad Men,” a sense of dread pervades the article. “Nations said farewell to a year of violence, tension, and economic uncertainty,” it reminds readers, who will soon discover that the new year brings even more lurid violence than the one just past. The accompanying photograph shows two people, backs to the camera, umbrellas open against a snowstorm, walking through a deserted Central Park. It’s bleak.

That was America, 1968. By comparison, the America of 2013 is downright quiescent. “No one is burning down cities,” says author Rick Perlstein, whose “Nixonland: The Rise of a President and the Fracturing of America” is a history of the political convulsions of the earlier time. “The national guard isn’t shooting anyone. You don’t have thousands of people on college campuses pledging themselves to sedition against the United States. You don’t have civil rights activists being murdered or churches being bombed. You don’t have draft resistance. You don’t have a string of political assassinations. In that sense, what’s happening now doesn’t compare to the 1960s.”

In fact, the 1960s marked a low point of congressional polarization; as the country was coming apart, Washington was working overtime to pull it together. When today’s Beltway graybeards long for the comity of the “Mad Men” era, they are recalling a political system in which polarization flowed into Washington, was more or less homogenized by the establishment, and then flowed back out as consensus. What we have today might be called the “Mad Congress” era: Relative calm flows into the capital, angry polarization flows out....