Michael Barone schools us in Chicago politics and the Weather Underground.
"For Obama, the outsider who gained the trust of the insiders, the position is different. He was willing to use Ayers and ally with him despite his terrorist past and lack of repentance. An unrepentant terrorist, who bragged of bombing the U.S. Capitol and the Pentagon, was a fit associate. Ayers evidently helped Obama gain insider status in Chicago civic life and politics--how much, we can't be sure. But most American politicians would not have chosen to associate with a man with Ayers's past or of Ayers's beliefs. It's something voters might reasonably want to take into account."