John F. Kennedy was a political leader who knew how to make
emotional contact with his audience. A few weeks before the
debates, Kennedy trailed Nixon in the polls, 53 to 47 percent.

By election day, Kennedy not only caught up with, but nosed ahead
of Nixon. Historians attribute Kennedy's narrow 1960 victory over
Richard Nixon to their televised debates - a view shared by Kennedy
himself, who said, "It was TV more than anything else that turned the tide."

1 It was generally agreed that Richard Nixon (like Mondale and Dukakis
 in later debates) "won" the debates on radio. He won on debating points.
 Yet it was Kennedy who emerged victorious among TV viewers.

When Nixon arrived at the Chicago television studio for the first debate,
he was haggard and drawn-looking because of intense campaigning
combined with a recent hospitalization for a knee injury, from which he had
not yet fully recovered. He had lost twenty pounds, and was not feeling well.
He had spent five hours stuffing his head with answers to potential questions.

During the debate, he sweated profusely under the studio lights,
streaking the pallid "Lazy Shave" makeup that was supposed to hide the deep
five o'clock shadow on his jowls. Even though Nixon's discussion of the issues
was cogent, and his grasp of events and factual detail was authoritative,
all the viewers could recall of the debates was the image of a candidate
who perspired under pressure, whose eyes darted during questioning,
who seemed to lack confidence and poise.
 
 

From: http://www.joshhunt.com/believe2.html