It is an interesting comment on our day that one of the more popular individuals on college campuses is not a brawny athlete, a punk-rock musician, or a handsome movie idol. Instead he is an average-looking, shy, sometimes sarcastic 38-year-old Indianapolis-born late-night talk-show host named David Letterman. The show - which airs Monday through Thursday on NBC-TV following ''The Tonight Show'' - has about 2.5 million viewers, according to Nielsen ratings, and that figure doesn't include his loyal college fans.
Last year, when the NBC affiliate in Baton Rouge, La., took Letterman's program off the air, protesting students organized pickets at nearby Louisiana State University and turned over thousands of signatures. The show was quickly reinstated, and the station president told assembled reporters: ''If that many people care about this show, it deserves to be on!''
Last April, Letterman received the eighth annual ''Jack Benny Award'' of the University of California at Los Angeles, joining former winners such as Johnny Carson, Joan Rivers, and George Burns.
Letterman's humor is described as low-key and slightly irreverent. Letterman himself describes his humor as ''observational and just plain silliness.''
Personally, he is not flashy nor does he encourage adulation. One colleague calls Letterman ''the TV star without the limo,'' since Letterman drives his own car to work rather than accept the network limousine. Letterman's confessed shyness may help fend off the tension of the show business.
''There aren't many people in show business I really admire,'' he says, though he quickly admits there are exceptions. Most notably, Johnny Carson.
His conscious ''distance'' from much of the bustle of the entertainment world is a sign of his style. Even as a youth, he says, he was not, like many comedians, the showoff or class clown. Instead, he spent his time egging them on.
It would be a mistake to think Letterman just a sophomoric wisecracker. He has a quick wit and a remarkable ability to find the human element in any situation. Though he does pick on a guest from time to time, he is at his best when he is not laughing at them, but with them. Particularly refreshing is his lack of coarseness.
Looking down on the traffic from his office on the 14th floor at 30 Rockefeller Plaza, Letterman admits he has not adjusted well to the push and shove of New York City. After many unsuccessful attempts at living in Manhattan he has moved to Connecticut. Apologizing for the interview's late start, Letterman remarks wryly: ''It took me an hour and a half to get to work this morning, and I don't even live in the city.''
The format of his show is like Johnny Carson's - part interview, larger part comedy. Occasonally the show has a ''theme,'' like the night it was broadcast from Letterman's living room. The show that won the Emmy award was what the writers call a ''custom made'' show. The audience was given a multiple- choice roster of items to choose from - like what kind of opening theme music would be played or what type of furniture would be used on the set.
Letterman's guests are often people not usually found on other talk shows. Recently Bob Dylan appeared for a rare interview. Then there was 78-year-old Editha Merrill, who singlehandedly landed a twin engine plane when the pilot collapsed at the controls; the Rev. Jesse Jackson; ''Doorman of the Year'' Sidney Miller of Fort Lee, N.J.; Graham Chapman of ''Monty Python'' fame.
Letterman show regular Larry (Bud) Melman is often used in staged antics like welcoming strangers at New York City's Port Authority bus terminal, handing them a steaming hot towel, ''courtesy of 'Late Night.' ''
If it appears Letterman has arrived from nowhere, quite the reverse is true. He has been on the comedy scene for some 12 years, having come to national prominence after his work at The Comedy Store Theater in Los Angeles. From that stage he became a regular on Mary Tyler Moore's variety program and also appeared on ''Mork and Mindy.'' When Johnny Carson's talent scouts asked him to appear on ''The Tonight Show'' and, soon after, to substitute as host, he leaped into that larger arena that brought him into the lives of millions.
Next, his own morning comedy/guest show was put together by NBC but soon canceled. He describes this time as ''a very unpleasant part of my life. I was on my own, and I actually got to the point where I didn't think it (that kind of opportunity) was going to happen (again).'' But almost a year later a call came from Fred Silverman, then president at NBC. He proposed that Letterman be kept on a retainer in case Tom Snyder left ''The Tomorrow Show.'' Snyder did leave, and in February 1982, ''Late Night With David Letterman'' went on the air.
As for speculation about Letterman's mark on TV comedy, his ''observational'' humor, unusual guests, and eagerness to innovate may give him what's needed to duplicate the staying power of Steve Allen and Johnny Carson before him. It's just possible, then, that David Letterman is more than the current campus hero. His comic talent may yet make all America laugh.