Surveys showed, though, that most of the people who listened on the radio thought Nixon won. It was the first time a nominee's appearance may have affected voters.
Some of those who played a role in the debate marked Sunday's anniversary by sharing their memories.
"Well, everybody was very surprised, including Vice President Nixon's own staff, that he agreed to the debate. Usually, the person who is ahead, and in this case, Vice President Nixon was way ahead of Kennedy, was shocked that he agreed to the debates," said Newton Minow, a former FCC chairman who was the debate's negotiator.
Minow says he never imagined the 1960 debates would have such an impact.
Minow and original debate journalist Sander Vanocur shared their recollections at a celebration organized by the Museum of Broadcast Communications.