Who Will Be the Ultimate Weapon in Late-Night War? : Television: While Arsenio Hall grins, ABC throws Rick Dees into the fray and CBS tries to keep affiliates from jumping ship.

Television’s late-night battleground is about to flare up again with new contenders trying to emulate Arsenio Hall’s success and fill the gap of Pat Sajak’s defunct CBS talk show.

Los Angeles disc jockey Rick Dees enters the arena the week of July 16 with a new ABC variety series that will follow Ted Koppel’s “Nightline.”

CBS, which is holding its annual affiliates meeting today and Friday at the Century Plaza, is expected to announce new shows to fill the gap left by the Sajak series--and stem the defection of its stations in the profitable late hours.

The fierce competition points up vividly the importance of Johnny Carson and David Letterman to NBC, the only securely anchored network around the midnight hour and thereafter. Despite the brilliance of “Nightline,” it has given ABC only 30 minutes of late-night programming.

Hall’s impact was felt dramatically when a station in St. Louis, the nation’s 18th biggest TV market, disclosed recently that it is planning to drop “Nightline” and replace it with Hall’s show. The station said it regretted losing “Nightline” but that Hall was hot and ABC would not allow the Koppel series to be pushed back 90 minutes.

While Hall’s show runs only one hour, it is being packaged in some markets in the future with a 30-minute variety series starring Nia Peeples--with both programs coming out of Paramount, which is handling the sales.

“ ‘The Arsenio Hall Show’ is one of the hottest properties in syndication and has the potential to be the late-night franchise going into the future,” said Wayne Thomas, general manager of the St. Louis station, KTVI, adding that he hoped an arrangement could be worked out with ABC to keep “Nightline.”

ABC’s gamble on Dees is a big one. The network is formidable on almost all fronts--”Good Morning America,” daytime programming, Peter Jennings’ nightly news and prime time--but it has been unsuccessful for years in trying to find a late-night series that could follow “Nightline” and allow ABC to tap into the profit center of TV’s wee hours.

ABC’s best move in this area came several years ago when it tried to lure Larry King away from CNN. The idea, says the CNN star, was to have him follow “Nightline” so that ABC could boast the tandem of Koppel and King--in short, TV’s two top interviewers. But King opted to remain with CNN, as he also did recently when CBS approached him to do a late-night series.

So now, for ABC, it’s up to the new series “Into the Night Starring Rick Dees”--a seemingly unlikely, incompatible pairing with the distinguished Koppel.

But Hall, who has clearly energized late-night, apparently has encouraged the belief that it is open to freshness and that anything is possible. And summer seems a logical time for ABC to give Dees a shot.

The situation at CBS is far more dire. Last in prime time, last with “CBS This Morning,” no longer first with Dan Rather’s nightly news, the network finds some solace from good ratings with its daytime shows, but even there its young female demographics are not as good as ABC’s. And now the void left by the Sajak show leaves CBS with another major problem to solve.

For a while, CBS filled the slot nicely by rerunning multipart stories from an admired crime series, “Wiseguy.” But it was a stopgap measure that predictably brought CBS station-clearance headaches from its affiliates, some of whom also pushed the late-hour lineup even further back into the night.

Now the network must find something more permanent, and among the reported entries for its late-night future are a series from producer Norman Lear, several action-adventure programs and, starting next month, a group of talk-show hosts trying out to see who does best. Lear was behind two memorable late-night comedies, “Mary Hartman, Mary Hartman” and “Fernwood 2-Night.”

A winning late-night lineup is critical to TV stations because it provides an attractive “lead-out” to news programs--meaning, for instance, that viewers may tune in an 11 p.m. newscast on KNBC Channel 4 knowing that Carson will follow. Or they may watch the 11 p.m. news on KABC Channel 7 while waiting for Koppel’s “Nightline.”

Since local news is a primary image of most TV stations and a chief source of their income, the late-night lineups that follow impact heavily on their revenues. At KTVI in St. Louis, general manager Thomas said that acquiring Arsenio Hall would “help our news audience.”

Thus CBS’ highest priorities these days--besides developing a winning prime-time schedule--include building a solid late-night program block to secure its relationship with its affiliates, who are the backbone of a network.

At the moment, Hall, though syndicated, has a much stronger late-night presence than CBS. ABC’s Koppel is also stronger. And NBC’s team of Carson, Letterman and all-pro “Tonight” sub Jay Leno takes on special meaning as a uniquely dependable area of programming for the network’s member stations.