David Letterman at a boil -- Why is the host of ''Late Night'' so angry?

Earlier this month some 25 million people watched David Letterman celebrate his 10th anniversary as NBC’s cranky czar of late night in a 90-minute prime- time special. But beneath the show’s celebratory mood was a persistent strain of dissatisfaction. Since NBC passed him over as Johnny Carson’s successor in favor of Jay Leno, Letterman has embarked on an unusually public campaign of vitriol, and most of the vintage whine has been poured over the network and its parent company, General Electric. Letterman has been everywhere lately — cordially griping on The Tonight Show, detailing his winter of discontent to Barbara Walters, and articulating annoyance in The New York Times and The Washington Post.

With Late Night a solid ratings success, and with NBC Entertainment president Warren Littlefield courting him to renew his contract (expiring in April 1993), Letterman should be on top of the world. So why isn’t he? Here’s our report on some current theories:

1. He’s complaining in order to extract a better deal from NBC.
Nobody denies that Letterman’s reportedly $10 million salary is already hefty. ”I think Dave’s amused when he reads articles that underestimate his salary,” says Late Night head writer Steve O’Donnell. ”He gets to lean back in his chair and have a good, hearty laugh.” But more than money may be at issue. Letterman has long voiced his impatience with GE’s scrimp-and-save policies. ”It’s one strange outrage after another,” says O’Donnell. ”It’s use of the studio. It’s audience ticket problems. It’s everything that makes it seem that the program’s not being treated the way it deserves.”

”There’s a whole laundry list of things that were irritating,” says Letterman’s manager, Jack Rollins, who adds that 1992 is not too soon to negotiate. ”Why is it early? If the complaints are there, they’re made when we feel put out. When else are you gonna make ’em?”

2. He’s fishing for an offer from ABC.
Rumor has it that Letterman is interested in the larger audience that ABC’s midnight slot could offer. ”ABC would love to do it as a blocking measure (against NBC’s late-night schedule),” says Paul Schulman, president of a company that buys network time for advertisers. But ABC’s very young audience might not match Letterman’s aging baby-boomer constituency. ”It’s probable that (Letterman) is exactly where he should be,” says Schulman. ”Often, a performer will work very well on one network and not another.”

3. He’s genuinely angry
Letterman’s grievances may go far beyond the Tonight Show flap to include a roster of real and perceived slights. Chief among them was NBC’s recent sale of Late Night reruns to the Arts & Entertainment Network, a deal in which Letterman was not invited to participate. ”Dave wished he could have been involved with the A&E deal more,” says O’Donnell. ”It’s not so much what happened as how it happened, without consulting or asking.”

4. He’s just being Dave.
Some suggest that Letterman’s public irritability is just show biz — a deft extension of his crankiest-man-alive style into the realm of publicity. ”The contract stuff is part of his public persona,” insists NBC weatherman Al Roker, who recently interviewed Letterman. In fact, Letterman’s grumpiness has taken on a somewhat traditional air; in interviews as far back as 1986, he can be heard vowing never to do another anniversary special. These days, even GE executives are said to look benignly on his constant jabs (”From what I understand, they kind of enjoy it,” says one insider). And head writer O’Donnell says Letterman will carry the contract routine only so far: ”We’ve written jokes where there’s a spilled coffee and he takes his NBC contract and mops it up, or there’s a small electrical fire backstage that he beats out with his contract. He’s rejected all those. He’s not going to use that in a formal way.”

At least, not this year. But if Letterman’s negotiations don’t proceed smoothly, Stupid Contract Tricks could become Late Night‘s last, best running gag.