Since earning a doctorate in education at Columbia in 1987, Mr. Ayers has been a professor of education at the University of Illinois at Chicago, the author or editor of 15 books, and an advocate of school reform.

Steve Chapman, a columnist for The Chicago Tribune, defended Mr. Obama’s relationship with the Rev. Jeremiah A. Wright Jr., his longtime pastor, whose black liberation theology and “God damn America” sermon became notorious last spring. But he denounced Mr. Obama for associating with Mr. Ayers, whom he said the University of Illinois should never have hired.

“I don’t think there’s a statute of limitations on terrorist bombings,” Mr. Chapman said in an interview.

The Schools Project

The Ayers-Obama connection first came to public attention last spring, when both Senator Hilary Rodham Clinton, Mr. Obama’s Democratic primary rival, and Mr. McCain brought it up. the archives of the Chicago Annenberg Challenge at the University of Illinois were opened to rese