Certainly it was an important moment in the election of 1960. But pivotal? Maybe, maybe not. The Museum of Broadcast Communications puts it this way: "The Great Debates marked television's grand entrance into presidential politics. They afforded the first real opportunity for voters to see their candidates in competition, and the visual contrast was dramatic. In August, Nixon had seriously injured his knee and spent two weeks in the hospital. By the time of the first debate he was still twenty pounds underweight, his pallor still poor. He arrived at the debate in an ill-fitting shirt, and refused make-up to improve his color and lighten his perpetual 5 o'clock shadow. Kennedy, by contrast, had spent early September campaigning in California. He was tan and confident and well-rested. 'I had never seen him looking so fit,' Nixon later wrote.
"In substance, the candidates were much more evenly matched. Indeed, those who heard the first debate on the radio pronounced Nixon the winner. But the 70 million who watched television saw a candidate still sickly and obviously discomforted by Kennedy's smooth delivery and charisma... Studies of the audience indicated that, among television viewers, Kennedy was perceived the winner of the first debate by a very large margin.
"...Commentators broadly agreed that the first debate accelerated Democratic support for Kennedy. In hindsight, however, it seems the debates were not, as once thought, the turning-point in the election. Rather than encouraging viewers to change their vote, the debates appear to have simply solidified prior allegiances..."