| Perhaps he refused to have a professional make-up artist do the work.
According to what I recall from my history instructors, he used a product then on the market called "Lazy Shave" rather than grooming himself more appropriately. It was essentially a wax-based foundation designed to hide five-o'clock shadow. Under the heat of the television lights, it melted.
Interviews of Americans who listened to the Nixon/Kennedy debate on radio, rather than watching it televised showed Nixon to be the favorite. Kennedy's more polished looks appealed to TV viewers. It's also likely that TV viewers at the time were closer to Kennedy's age than Nixon's. | 
