Dawning of a New Dave

"Expect the unexpected," a publicity slogan promised, when David Letterman began as "Late Night" television host on NBC nearly 15 years ago. Appearing in the wee hours of the morning, the comedian pioneered a wacky humor that transformed television comedy.

"David Letterman brought to American television a freewheeling, absurdist quality," says Ron Simon, curator at New York's Museum of Television and Radio. It was such a hip hit that Mr. Letterman's switch to CBS in 1993 made front-page news. His first shows for CBS enjoyed mega-ratings.

Now the unexpected has struck again. For the 52-week period that just ended, the "Late Show with David Letterman," with an average 3.9 rating and 11 share, was topped by his rival, NBC's "Tonight Show with Jay Leno" at an average 4.7 rating and 14 share. (Nielsen Media Research defines each rating point as 959,000 homes.)

In an attempt to lure viewers back, the "Late Show" promoted a "specialty" show broadcast on Sept. 20, a one-hour telecast without commercial breaks. For the first time since Dec. 20, 1995, the Letterman show beat the Tonight Show (among regularly scheduled shows). The Late Show averaged a 6.3 Nielson rating, while Leno earned a 5.8 rating. "We're always looking for ways to keep the "Late Show" fun and interesting," executive producer Rob Burnett says.

The "no-break" telecast showcased favorite "Late Night" bits. In one Stupid Pet Trick, a pit bull clamped a hanging rope in its teeth and spun around while twirling a hula hoop. The most successful segment was a taped "remote" - an on-location shoot where the camera roams Mr. Letterman's Neighborhood seeking colorful characters. A boy gleefully showed off his talent for honking like a car horn.

Funny but not exactly fresh.

In the past, Letterman scored inventive triumphs with specialty shows. He won an Emmy in 1994 for the "Custom Made Show," where the studio audience voted on jokes, guests, music, and even selected Letterman's wardrobe. He once did a Christmas special six months early "to beat the rush."

The man who pioneered situational comedy - like covering himself in potato chips to be lowered into a vat of onion dip - is now in the position of being hoist by his own petard. "The Late Show" was such a big success, but now it follows a formula," says David Schwartz, film and television curator at the American Museum of the Moving Image in Queens. Under former executive producer Robert Morton (replaced in March by Burnett), "It got predictable and didn't seem to be taking many risks."

"It's not Letterman who changed but the audience," says Robert Thompson, associate professor of TV at Syracuse University's Newhouse School of Public Communications. When the comic started in 1982, "his show was so different and audacious, breaking all the rules, that only the hippest people understood.... He transformed the medium; then like anything groundbreaking, he became old hat."

In contrast, Leno uses a traditional stand-up approach, with set-up lines followed by punch lines. Leno's emphasis on topical humor, rather than "out-there" innovation, is more universal.

Letterman tried to freshen his act and broaden his appeal when he moved to the earlier time slot. He gussied himself up with tailored, double-breasted suits. He toned down his crankiness, which had actress Sharon Stone weeping in the Green Room after he made a dumb-blonde putdown. His ratings peaked during the 1994 Winter Olympics at 8.9 (his average before had been 5.8). Then came the debacle of the 1995 Academy Awards, where Letterman's mocking wordplay ("Oprah ... Uma") as host bombed with the prime-time audience.

Now the talk-show host jokes in "Top 10 Signs I, David Letterman, Am Getting Old": "I can't stay up late enough to watch my own show."

More seriously, the No. 1 sign that his show is getting old is its own history. The anti-establishment rebel who called NBC executives "pinheads" and whose reputation depended on debunking institutions, has become an institution. "The show is in transition," Ron Simon says. "We know the old Dave, and have yet to discover what the new Dave will be like."