"Smokey and the Bandit," the runner-up hit of three summers ago (the summer of "Stars Wars") was a happy accident. No one was impressed by the original script. Nothing special was expected at the box office.

But Burt Reynolds recruited Sally Field for the project, and they emerged as a fresh, winning romantic comedy team. And Hal Needham, directing his first feature after a 20-year career as a stunt man, appeared raring to go: The movie was a streamlined, happy-go-lucky triumph.

The company must have been lucky and inspired the first time around, because the inevitable sequel -- "Smokey and the Bandit II," which opens today, at area theaters -- is a premeditated embarrassment. It seems to prove that entertainers who discover a successful formula may not have the foggiest notion of how to protect, duplicate and sustain it.

Someone insisted on giving the sequel what was probably described as "a new dimension" by tinkering with the character of the hero. I suspect Reynolds may have been the selfdefeating instigator of this miscalculation.

As originally characterized, Bandit was a resourceful, dashing modern saddle tramp, an independent trucker who could never resist an outrageous sporting proposition. In the first movie, he agreed to drive from Atlanta to Texarkana and return with a shipment of Coors within 28 hours.

A human equivalent of the Roadrunner, Bandit was designed for excapist kicks rather than psychological insight. His only real problem was winning the wager, which demanded that even romance blossom at an accelerated pace. But in the sequel everything is subordinated to the tiresome question of whether or not poor Bandit, who has inexplicably gone to the dogs between pictures, can pull himself together and become his own best friend.

At the end of "Smokey and the Banit," the hero and his sidekicks, Sally Field as a runaway bride named Carie and Jerry Reed as a trucker named Cledus, were supposed to be bound for Boston, having accepted a new wager to return to Atlanta with a bowl of clam chowder within 18 hours.

In the sequel, Pat McCormick and Paul Williams return as Big Enos and Little Enos Burdette, a ridiculous father-and-son team of Texas fat cats who propose the new race from Florida to Dallas.This time the Burdettes wish to deliver a symbolic gift -- a live elephant -- to the Republican National Convention.

Before the trip can begin, Bandit must be placed back on his feet. A lot of unfortunate things have supposedly happened since we last saw Bandit and his friends depart for Boston. Catching up with this trumped-up soap opera history makes for a deadening earful of second-hand exposition. The movie never recovers from his self-inflicted dramatic handicap.

It seems that Bandit became a big celebrity and developed a swelled head. His behavior alienated Carrie, who is reintroduced almost going through with the marriage she ran away from originally, an unthinkable union with Mike Henry, the dumbell son of Jackie Gleason, a choleric Texas sheriff named Buford T. Justice.

Answering an SOS from Cledus, the bride leaves her baffled groom at the altar for a second time and rushes to Florida to help rehabilitate Bandit, deep in a beer stupor. The dubious idea of portraying Bandit as a pyschological cripple is magnified by dragging out his equally contrived rehabilitation over the length of the picture.

We're supposed to believe that Bandit has recovered when he places the safety of the elephant above profit. To be specific, he risks missing the deadline for delivery set by the Burdettes in order to permit the elephant, a pregnant passenger, to have her baby.

"I like myself, Carrie," Banit declares. "I found out there was something more important than me."

That's what he thinks. The film-makers are so oblivious to the practical problems and opportunities presented by the situations they fabricate that self-congratulation is the last thing the hero should be allowed to express. For openers, the elephant is found inside a crate in a warehouse, where she has supposedly been stashed for weeks before the heroes locate her and considerately wedge her into a truck. For closers, Bandit sleeps through the birth of the baby elephant. It seems unlikely that the film's writers tested this idea before using it. Offhand, I can't recall another movie that exploited an animal with such maddening disregard for common sense and decency.

Far from being complicated, the character of Bandit is diminished by the caddish shadings imposed on him in "smokey II." One gets the uneasy feeling that Reynolds wanted to disarm personal criticism by putting himself down, as he often does in television appearances. The revised Bandit seems to represent a complacently unflattering self-image -- the conceited show-biz wretch Reynolds sometimes fears he may become.

No one is in top form. The dreary exposition seems to defeat Needham. The only time his direction loosens up is during the stunt finale, where he's suddenly free to orchestrate the movements of dozens of vehicles. Meanwhile, the actors stand around trading banal recriminations or belaboring comedy shtick.

Gleason's sheriff has grown coarser, as if to overcompensate for the listless atmosphere and feebly rationalized plot. Sally Field looks as if she had just gotten through trying to talk everyone into getting down to business, to no avail. Dom Deluise, a newcomer to the troop, also fails to distinguish himself as an ethnic veterianarian.

It seems deplorable but appropriate that the end titles are illustrated not with scenes from the film but with out-takes. The whole movie sugguests a feature-length outtake, something tossed off by professionals unable to get in the mood for working.