“A Love Song For Bobby Long” is a shake ‘n’ bake film whose modest pleasures only just compensate for the many chances it squanders. Shainee Gabel’s second feature has all the elements of a colorful character study: an eccentric older writer, a headstrong young beauty, a dead lover, a family mystery, a New Orleans denizened by affable grotesques. Intentionally sidestepping the obvious warp of these elements—think Tennessee Williams, “Midnight In The Garden Of Good And Evil”, even the recent remake of “The Ladykillers”—Gabel chose to keep the tone earthy and low-key. The Southern eccentricities are minimized, the universal drama kept on the front burner. The movie is bright and intelligent. If its hold on Southern vernacular is completely inauthentic the characters aren’t devoid of all sympathy.

Gabel’s direction is the big flaw. Too often “Bobby Long” plays like a softie afraid of its own innate violence. For one thing, the film’s rapier dialogue hits home with no resistance. Instead of “His Girl Friday” exchanges, in which two invulnerable wits spar without seeming to land punches, Bobby and Pursy bruise up far too easily. Bobby’s silver-tongued vulgarities flicker and burn in the first round and vanish in the second. Pursy has a good uppercut (“You must know about men”, goads Bobby, to which she retorts “Yeah, but not old ones”) but no defense. During a sequence in which Bobby tells a shaggy dog tale of his youth, for instance, Gabel keeps cutting back to Pursy’s reactions—she feigns indifference, is piqued, then annoyed, finally scandalized into leaving in a huff. These reaction shots attenuate the free flow of wit. The scenes develop a seesaw sameness: A quips while B frowns, then B quips back while A frowns. The transparency of emotion makes for bald, predictable melodrama.

Here’s where the star power comes in. John Travolta and Scarlett Johansson make such a watchable pair they manage to salvage the film on glamour alone. Travolta is bigger than any role he plays to begin with. Like Nicholson or Pacino, he is always 90% himself and 10% whatever character he’s playing. Here he combines the mesmerizing Southern charm of the Clinton-esque pol in “Primary Colors” with the sharp, boozy edges of a Stanley Kowalski. Gabel gives him most of the few extended takes in the film, letting him chew the scenery and the catering table to boot. Few actors are better at that (only Al Pacinio comes to mind).

Travolta is hardly convincing as a self-destructive alcoholic, though. In most of the scenes he looks like he’s adopting a pose solely to goad Pursy. And even when he’s savaging her with his honeyed drawl, there’s a generous twinkle in his eyes like the one in the eyes of Vincent Vega and Chili Palmer. Travolta is bigger than life, everything we ask of our movie stars. Provided he picks the right script—always chancy with him—he delivers like gangbusters.

Johansson is no less than the finest actress of her generation. She hasn’t strayed far from a certain kind of role—introspective young women in search of themselves—but what she does she does well. In “Bobby Long”, she mauls the role, and I mean that as a compliment. Her beauty and sophistication are wrong for the part of a white trash orphan—in some scenes she resembles a Victoria’s Secret model, in others a strawberry-blonde Marilyn Monroe—but the grace and aplomb with which she inhabits the role of Pursy pulls the movie into line with the blaze of her beauty. The unique combination of otherworldly looks and effortless talent suggests Grace Kelly, a fact which thus far only Sofia Coppola has really exploited successfully.

But Coppola had a nuanced, if laconic script. In Gabel’s film the writing is more artificial, a clothesline upon which Johansson hangs a small but colorful wardrobe of tics. As she did in “Lost In Translation”, she imbues her character with a rich inner life with just a wry turn of her lips or a fold of her arms. The tender spasms of her neck muscles as she fights tears is the stuff of top-shelf vampire pornography. She and Travlota create the spectacle of two gigantic stars dwarfing a lesser movie, an object lesson in the necessity of the unquantifiable It in filmmaking.