Annette Bening is downright giddy in "Being Julia," and I'm not sure if it's because she left Warren at home with the kids or because she's sinking her teeth into the kind of role that comes around once in a career. That role, an imperiously swooning drama queen of a stage star, is more fun than the movie, and so is Bening. You can feel her drag "Being Julia" uphill for an hour and a half until the final 15 minutes, when the ground finally levels out and the picture becomes fine, vengeful fun. This isn't just acting, it's a tractor pull. Do they give out Oscars for that?
The title of "Being Julia" presupposes that there's only one Julia Lambert, but the onscreen evidence suggests there are as many as there are breaths in a day. A hugely successful star of London's West End in the late 1930s, Julia is never not acting. She's also a little bored with her latest vehicle and a little terrified of getting old.
The men who swarm about her aren't any help. They include her director-husband Michael Gosselyn (Jeremy Irons), with whom Julia maintains a discreet and indulgent distance; their remarkably tolerant teenage son, Roger (Tom Sturridge); a worshipful British Lord (Bruce Greenwood); the roistering ghost of her acting teacher (Michael Gambon), who shouts directions for stage and life that only she can hear; and, by default, the play's financial backer, Dolly De Vries (that marvelous pop-eyed walrus Miriam Margolyes), who's overly fond of dropping in on Julia during the star's massage sessions.
A young American named Tom Fennel (Shaun Evans) would seem to be a mere lapdog in this company, and for the longest time Julia treats him as such. But her insecurities mount, the boy is impetuous, and before long she and he are dallying in his garret. No, it's not believable, but it's what the plot calls for, and Bening's a trouper to put it over.
There's more: a sultry blonde gooney bird of a young actress named Avice (pronounced "Avis" and played by Lucy Punch) who suddenly seems poised to steal men, a new play, and -- worst of all -- the spotlight from Julia. Avice's secret weapon is that she's smarter than people take her for. Her weakness is that she's still pretty dumb.
It's harsh but accurate to say that's true of the movie as well. Oddly, some swank people are responsible for this souffle: Istvan Szabo, the Hungarian director of "Mephisto" and "Sunshine"; Ronald Harwood, Oscar-winning writer of "The Pianist"; W. Somerset Maugham, upon whose 1937 novel "Theatre" the movie is based. The costumes, sets, and music drip with borrowed Merchant-Ivory opulence. For all the effort, "Being Julia" stays on the page. It's fussy and plot-bound, lacking the rapturous venom of "All About Eve," the backstage classic it aspires to. You never have to fasten your seat belts, and that's a problem.
Still, the final act is an expertly constructed bit of farce that pays off beautifully, sending you home convinced you've seen a better movie than was there. Pockets of the film hide some sharp acting: Juliet Stevenson as Julia's trusted dresser, for instance. Irons does what he can, and he's a morally backsliding joy to behold, but he's not onscreen enough.
Anyway, this is Bening's field day, and she fends off all comers with a performance that's astonishing for both its happy invention and technical overkill. Julia flits, flirts, gives in to passion, draws aside to panic, puts on the mask again, schemes, droops, and triumphs, and by the final scenes role and performance are reflecting each other in an infinite hall of mirrors. This is as dazzling as comebacks get, but you're never sure if you're watching a woman who'd do anything for an audience or an actress who'd do anything for an Oscar.
Ty Burr can be reached at tburr@globe.com.