On this day (Sept 26th), in 1960, Nixon and Kennedy squared off for the first televised presidential debate. This was not just the first televised debate for them (they would participate in four debates), but the first televised presidential debate in America’s history.
The GILDER LEHRMAN INSTITUTE OF AMERICAN HISTORY put it best when they described the importance of this change in political debate.
“The Kennedy-Nixon debates stand out as a remarkable moment in the nation’s political history, not only because they propelled an unlikely candidate to victory, but also because they ushered in an era in which television dominated the electoral process. Recalling the nineteenth-century tradition of “front porch” campaigns in which groups of citizens traveled to a presidential candidate’s home to meet him and question him about the issues, Charles Kuralt of CBS News declared that Kennedy’s skill with the medium helped to make television the nation’s new ‘front porch.'”
The two candidates took the opportunity to debate the issues of the day. The greatest of these topics was the topic of national security. The Cold War was heating up, and the space race was underway. Both debated equally on strengthening the U.S. military and thwarting the threat of communism. Though there wasn’t much debating. The New York Times said:
“For the most part, the exchanges were distinguished by a suavity, earnestness and courtesy that suggested that the two men were more concerned about ‘image projection’ to their huge television audience than about scoring debating points.”
While the first of these four debates was slow and the majority of radio listeners believed the debate to have been a draw, the majority of the seventy-million watching the debate on television declared Kennedy the clear victor. Less than two months later, the election came to an end, and Kennedy won the presidency. With the popular vote 49.7 percent to 49.5 percent, it could easily be said that the “Great Debates,” that had made history as a first, was a deciding factor. Of people polled, six percent claimed that the televised debates directly led to their voting decision. 
If you want to watch the entire first debate, here it is.