The marketing campaign for the new David O. Russell film, “Joy,” starring Jennifer Lawrence, has been extremely nervous about bringing down the party with the word “mop.” Mops traditionally do not sell at the multiplex. Mops traditionally are what clean up the multiplex.

But mops are central to the narrative in “Joy,” and there’s no way around it. Miracle Mop inventor and entrepreneur Joy Mangano, a working-class Long Island striver who’s now a multimillionaire in the realm of Home Shopping Network infomercials, serves as the subject of Russell’s ninth feature (if you count the long-shelved “Accidental Love”). Russell’s previous three pictures, “The Fighter,” “Silver Linings Playbook” and “American Hustle,” constitute a remarkable string of films that were A) popular, B) competitive in the awards season and C) really good.

“Joy” breaks the streak, unfortunately, though by now writer-director Russell has earned the right and the privilege to stumble and then go on making unconventional mainstream movies with terrific actors.

This one’s an uncertainly stylized success fable, narrated by Joy’s grandmother (Diane Ladd), revealing in its hectic early scenes a young girl (Isabella Crovetti-Cramp plays the young Joy) determined to construct things and make her mark without becoming the woman on some man’s arm. “I didn’t need a prince,” she tells us. She just needed her chance.

After inventing a retractable dog collar only to see the Hartz version zoom on the sales charts instead, Joy vows to retain control of her creations. Years later, bingo: the retractable, self-wringing mop, made of sturdy plastic and far less icky to use than mops that came before it. This mop becomes the means to a happy end. Bradley Cooper plays the QVC executive who backs her and then becomes her business adversary. Robert De Niro is Joy’s dad, whose auto body shop is converted into a makeshift factory. Isabella Rossellini is the De Niro character’s paramour and Joy’s backer.

“Joy” finds its footing in the simplest scenes of Joy being introduced to the wonderful world of infomercials. Then the movie hacks its way through backstage dramas involving patent controversy, unscrupulous business partners and impediments to Joy’s destiny. Edgar Ramirez portrays Joy’s ex-husband and near-constant friend and supporter. Virginia Madsen has too little to do as Joy’s wreck of a mother, obsessed with the soaps, worried about everything.

“Joy” does play like a movie of the moment: It’s about a woman who deals with a massive wall of male skepticism and derision, and takes care of business. Lawrence is very good in the role, as far as the role goes. But the script never jells; the comedy feels forced and mechanically boisterous, particularly in the crucial early passages. And in the final 30 minutes, it’s a dangling mess. If only 1980-era Jonathan Demme, the Demme of “Melvin and Howard,” had gotten hold of this story!

Then again, at his best, Russell is his own kind of ensemble wizard. This movie feels as if it got away from him. Audiences might buy it anyway; Lawrence’s extraordinary ease and skill never hurt. I’m not sure if hiding what the movie’s actually about, in the trailers, was the smartest idea. On the other hand, an affordable and cleverly designed mop will never be an easy sell in a universe where “Star Wars” is batting cleanup.