John McCain traces the rancorous tone of the presidential campaign back to last summer when he invited Barack Obama to have lots and lots of town-hall meetings with him all around the country. When Obama turned him down, obviously McCain had no choice but to start depicting his opponent as a terrorist-loving advocate of talking dirty to kindergarteners.

Finally this week, the two men did meet in a town-hall showdown, which turned out to be like all other debates, except with much less excitement and much more pacing around. It seems unlikely that many people switched off their TV sets and said: “Gee, I could sit through a dozen of these.”

McCain may feel compelled to go back to his guilt-by-association theme. And this has me feeling very guilty about my associates.

The McCain folks have been obsessed with William Ayers, a neighbor of Obama’s who is a professor at the University of Illinois at Chicago. Back in the 1960s, Ayers and his wife, Bernardine Dohrn, were leaders of the Weather Underground, an antiwar group whose penchant for violence was exceeded only by its haplessness. Ayers has since become an education expert and was named Chicago’s Citizen of the Year in 1997. He gave Obama a house party when Obama was running for the State Senate.