The emergence of Bill Ayers as a controversial figure during Wednesday night's debate between Barack Obama and Hillary Clinton reminded me of when Ayers came through Madison a couple of years ago and said something startling.

He said it to me and I was startled, anyway.

Ayers is currently a professor at the University of Illinois at Chicago. During the Vietnam War era, he was a member of the Weather Underground, a radical group that advocated and practiced violence against establishment targets.

Ayers was indicted in 1970 for inciting to riot and conspiracy to bomb government buildings, but he was never tried. He was a fugitive for more than a decade but, when he turned himself in, the charges were dropped due to misconduct by his pursuers.

"The Bureau had recklessly tapped phones," Ayers wrote in a 2001 memoir, "broken into people's homes, even written a plan to kidnap (his wife) Bernadine's infant nephew."

While promoting that book, titled "Fugitive Days," Ayers told the New York Times: "I don't regret setting bombs. I feel we didn't do enough."

During Wednesday night's debate, George Stephanopoulos of ABC News asked Obama about Ayers. Obama downplayed their relationship, saying that Ayers lives in his neighborhood but they're not close. He called Ayers "somebody who engaged in detestable acts when I was 8 years old."

Hillary Clinton then noted that Obama and Ayers had served together on the board of a do-gooder group in Chicago. Obama shot back that Clinton's husband had commuted the sentences of two other members of the Weather Underground, at which point the candidates pretty much moved on to other topics.

Ayers and his wife, Bernadine Dohrn, were in Madison in October 2006 for the Wisconsin Book Festival. They were promoting a new book, "Sing a Battle Song: The Revolutionary Poetry, Statements, and Communiques of the Weather Underground, 1970-1974."

I had a chance to interview Ayers prior to their appearance and he seemed to scale back just a bit from some of the more radical ideas of the Weathermen. He said neither he nor Dohrn were "nostalgic" for that era and that "some of the rhetoric" from that time "now seems overheated." But he added: "We continue to believe that empire building and occupation is wrong."

I wanted to interview Ayers for one reason: My enduring interest in whatever became of Leo Burt, Madison's most famous fugitive. Burt is more than that: He's the great unfinished story of my half century in this city.

Ayers had been underground for 11 years; Burt has now been a fugitive for nearly 38 years, since he and three others (all eventually apprehended) set off a bomb targeted at the Army Math Research Center in Sterling Hall on the UW-Madison campus. The 1970 blast killed a young researcher, Robert Fassnacht, and caused millions of dollars of damage.

When I began to ask Ayers about Burt, something unexpected happened. It became clear Ayers didn't realize Burt was still a fugitive. At that point, it had been 36 years.

"That's amazing," Ayers said, after I filled him in. Then he repeated it: "Amazing."

I said: "You really didn't know?"

"I remember who he is," Ayers said. "I'll be damned."

I guess I figured that '60s radicals would always keep tabs on each other, not like old high school teammates exactly, but one way or another.

I suppose it says less about Ayers than it does about my own obsession with Burt. I've written two long magazine pieces about him. The first was for Madison Magazine in 1996. It was memorable because I speculated that Burt was the Unabomber. The piece ran a few months before they caught the real Unabomber. In my defense, the Burt-as-Unabomber theory had also been embraced by Tom Bates, the author of "Rads," now deceased.

The other magazine story was for the Wisconsin Alumni Association's quarterly, On Wisconsin. It ran in the summer of 2005 on the 35th anniversary of the bombing and was perhaps most notable for something that happened during my research. While I was interviewing a retired FBI agent who had worked a decade on the case, he collapsed with a heart attack. I did nothing admirable other than call 911, but the Middleton EMTs were great. It was touch-and-go for 24 hours, but they saved his life.

We may yet get a definitive take on Burt if an Eastern writer named Joe Brennan Jr. ever publishes the book on Burt he's been researching for years. Tentatively titled "The Last Radical," I would have thought it might be out by now, but I 've lost touch with Brennan and have heard nothing lately.

Speaking of Burt, Bill Ayers told me: "If he has survived and led a decent life, that's good. I wouldn't want to see him caught."

I asked Ayers: "How hard was it staying underground?"

"It's difficult in some ways," he said. "In other ways, it was as easy as falling off a log."