A new battleground for viewers is emerging in cable television: late night.

On this battleground Jon Stewart is perhaps the most publicly decorated general, proving with "The Daily Show" on Comedy Central that there are at least 650,000 people each night who are prolonging their day -- or staving off the coming of the next -- by watching something other than local news or syndicated reruns of sitcoms on broadcast television at 11 p.m.

In recent weeks Comedy Central has moved to capitalize on Mr. Stewart's success by directly following "The Daily Show" with old "Saturday Night Live" shows instead of "Win Ben Stein's Money." With "Saturday Night Live" the Comedy Central audience from 11:30 p.m. to 12:30 a.m. has grown 40 percent since last year.

In August Comedy Central will begin showing a new Sunday-night block of late-night shows. "The Chris Wylde Show" at 11:30 will be a sort of variety show, with Mr. Wylde, the comic actor, as host. "Insomniac With Dave Attell," at midnight, will follow Mr. Attell, a comedian, as he explores various cities late at night.

But Comedy Central is not the only basic cable network looking for late-night success. Among others, E! has "Howard Stern"; MTV has "Undressed," the racy, Generation Y soap opera.

FX is trying to pull people away from broadcast television by running a new original program at 11 p.m. called "The Test," in which celebrity guests are questioned about sex, morals and etiquette. It is followed by reruns of the old Fox network variety show "In Living Color." Going by the FX ratings for last month, that combination helped it increase its audience in the
11-to-midnight time slot to 384,000 people this past June from 201,000 people in June 2000.

And now the USA network enters. Having lost professional wrestling last year, USA has been seemed to grope for a new programming direction. It has a seasoned new hand at its helm, Doug Herzog (who helped put "The Daily Show" and "South Park" on Comedy Central and "Malcolm in the Middle" on Fox), and he has decided to develop a late-night schedule at USA.

In "Smush," a new 11 p.m. show to be introduced this year, guests will be asked to divine strange word variations -- created by smushing words together -- through a series of clues. The network said it was working on another original show to follow "Smush," which has Michael Davies, the producer of ABC's "Who Wants to Be a Millionaire," as a producer.

The big question is whether these cable encroachments are a threat to Jay Leno on NBC and David Letterman on CBS. With average audiences well into the millions, their shows dwarf the cable competition in the ratings. Stacey Lynn Koerner, who analyzes television programming trends for TN Media, which helps companies buy television advertising time, said Mr. Letterman and Mr. Leno could probably continue in those dominant roles as long as they chose.

"A lot of these networks are very targeted," she said of the basic cable channels. She said the new late-night cable shows would probably be more of a threat to one another than to the big network shows.

"You have to temper all of this with the fact that we keep getting more and more choices, which fragments the audience," she said.