Writing in the New Yorker last month, Hendrik Hertzberg digs up this interesting history:
Television debates were a long time coming, and the road was rocky. The first nationally broadcast faceoff between Presidential candidates was on the radio, in 1948, between Thomas E. Dewey and Harold Stassen, who were contending for the Republican nomination. (Dewey insisted on a single topic for the entire hour: “Shall the Communist Party in the United States be outlawed?”) The first such debate to be televised, in 1956, was also an intra-party affair, between the Democratic rivals Adlai Stevenson and Estes Kefauver. Newton Minow, who was later President Kennedy’s chairman of the Federal Communications Commission (and won fame for calling television “a vast wasteland”), was Stevenson’s top aide, and it was largely his and Stevenson’s efforts that made possible the seminal Kennedy-Nixon debates. Newt Minow was also instrumental in reviving Presidential debates in 1976, after a sixteen-year hiatus, and in making them practically mandatory in every election since then.
via Presidential Debates, Citizens United, and the Politics of Media : The New Yorker.