As the newly divorced hero of "Starting Over," a delightful romantic comedy destined for enormous well-deserved popularity, Burt Reynolds reaches a breathtaking new plateau of screen acting dexterity.

This endearing characterization won't come as a shock to people who've been following Reynolds' progress and maturation from "Smokey and the Bandit" to "Semi-Tough" to "The End" to "Hooper," reinforced by Reynolds' expert performances as himself on the Johnny Carson show.

Reynolds has achieved such an uncanny humorous rapport with the camera that he might be unwise to refine his technique any further. In "Starting Over" his acting is exquisitely balanced: He never slips out of character, never fails to relate to the other performers, while simultaneously perfecting incisive, witty reactions meant for the eyes of the audience alone.

Reynolds navigates a tightrope that only the most experienced and astute film actors ever master. He communicates the introspective Phil Potter's frequently perplexed, ambivalent feelings in slight movements of the eyes, slight twinges in the set of his mouth, that contrive to look spontaneous and believable while also being gratuitously, irresistibly funny. Reynolds' pained, affectionate incredulity seems to draw us into Potter's thought processes by flashing the implicit question, "Did they just say what I thought they said?" or sometimes, "Did I just say what I heard myself saying?"

Playing a reserved, middle-class professional man, Reynolds denies himself the active physicality of his popular daredevil roles. Potter's masculine urges, aggressions and insecurities simmer behind a cautious, well-behaved facade and reveal themselves in those wittily neurotic facial expressions.

The movie begins with a scene of pillow talk. Over a composition of their neatly made-up bed we hear Jessica Potter (Candice Bergen) shock her husband with the news that she wants out of their marriage. An aspiring songwriter, Jessica tells Phil that she's "gotten a lot of terrific feedback" and longs to be "more than just a shadow of my man."

Potter is further dismayed by Jessica's confession that she's had an affair with his best friend. Leaving their New York apartment, Potter seeks refuge in Boston with his older brother Mickey, a psychiatrist (Charles Durning) and sister-in-law Marva (Frances Sternhagen). He's a little baffled by them too, sweet and well-meaning as they are. They seem to have mellowed out somewhat since Phil last encountered them.Could he be the only one not "going through exciting changes"?

Displaced and lonely, Phil rents an apartment, finds a job as an English instructor at a junior college, enrolls in a divorced men's encounter group and tries to meet other women. The breakthrough occurs when Mickey and Marva set him up with a friend of theirs, a nursery school teacher named Marilyn (Jill Clayburgh). Although the initial encounter is a comic disaster -- undermined by Marilyn's obsessive determination to protect herself from harm and establish rigid dating guidelines -- the acquaintance quickly ripens into a love affair.

Their budding contentment is threatened by the return of Jessica. Inexplicably, her songs have brought her fame, but somehow it all seems empty without the man she left behind. With rekindled dismay Phil realizes that he's vulnerable to her overtures. Marilyn is clearly the better mate, the better woman, the better person. It would be insane to risk hurting and losing her. Yet Jessica still has a hold on him.

Screenwriter James L. Brooks, one of the creators and sustainers of "The Mary Tyler Moore Show," achieves a theatrical film breakthrough on "Starting Over." He transforms a rather drab Dan Wakefield novel into a good-humored, heartening update of traditional romantic comedy. Brooks' sensibility is certainly more sentimental than Wakefield's, but in this case a little sentimentality is a welcome, humanizing inspiration.

Since Reynolds embodies a male variation on the heroine of Paul Mazursky's "An Unmarried Woman," it's peculiarly amusing and satisfying to see Jill Clayburgh assume the role of the hero's new romance. She makes Marilyn eccentrically adorable, a gangly, dowdy, deceptively defensive woman whose innate tenderness and romantic passion seem all the more touching and enchanting for breaking out of spinsterish defenses.

Reynolds and Clayburgh began an appealing chemistry in "Semi-Tough," and it's enhanced in the roles Brooks tailors for them. There's something magnetically funny and stirring about the way these two performers confront one another within the confines of the screen. You're not quite sure how or why it should be, but they constitute a match.

The script is structurally awkward in a few respects. It does not promptly establish Potter's profession (he's supposed to be a magazine writer) before he takes up exile in Boston. It would be preferable if the reappearance of Jessica were a climactic episode, coming after Phil and Marilyn had been living together for some time. Now it appears that the story is headed for a resolution when Phil perceives again what an incorrigible nitwit Jessica is, but suddenly he's backsliding again, and the crisis is strung out for an extra reel or so.

When the desired denouement appears, you're not so much overjoyed as relieved. Thankfully, the filmmakers find their way back.

"Starting Over" must have been a welcome relief from turgid seriousness for director Alan J. Pakula. While he lacks a natural light touch, his deliberation is often surprisingly witty and effective, especially with sight gags and Reynolds' minutest double-takes.

Anyway, "Starting Over" is vastly more pleasurable than "All the President's Men" and "Comes a Horseman." One of his minor triumphs is Candy Bergen's performance: For the first time, she is exploited with satirical zest, and it becomes her to impersonate a beautiful dope. You may not be quite sure how much of the performance is comic acting and how much sheer embodiment, but that doesn't make it less entertaining.

There's no doubt about Burt Reynolds' skill. "Starting Over" finds Reynolds at a level of proficiency that approaches the awesome. Only tragedy or utter folly can now prevent him from consolidating one of the great screen starring careers.