Is Robert De Niro back? Can it be true? It seemed for a long while there that we had lost the beloved tough guy actor forever to demeaning projects like “Dirty Grandpa” and blink-and-you’ll-miss-it boxing movies, but Taylor Hackford’s “The Comedian” shows promise for De Niro fans. It’s a truly lived-in, committed and sincere performance, playing an aging comic, Jackie Burke, who can’t manage to outpace his past starring as Eddie in the ’80s sitcom “Eddie’s Home.”

But Jackie just wants to be Jackie, not Eddie anymore. When a heckler taunts him into a confrontation at a gig, a video of the scuffle goes viral, and Jackie is sent to the clink for 30 days and tasked with community service. Somehow, that manages to be the turn upward for his career — and his life. Part of being Jackie — not Eddie — is freedom from the family-friendly sitcom leash, and he takes every opportunity to test those boundaries, plunging instantly into aggressive crowd work and ribald blue humor, whether he’s at a gig or not.

De Niro sells both the stand up, and the well-rounded performance of a man who’s always on, but searching for a deeper connection, whether he’d admit that or not. His relationships range from the strained (with his brother and sister-in-law, played by Danny DeVito and Patti LuPone), to the combative (with his manager Miller, played by Edie Falco) to the casual, friendly ribbing with the comics at the Comedy Cellar. So meeting Harmony (Leslie Mann) at the homeless shelter, where they’re both working off their court-mandated community service hours, offers the opportunity for something else.

The world of “The Comedian” feels authentic, with De Niro surrounded by real comedians and old compatriots alike. One can’t deny the thrill of watching De Niro and Harvey Keitel — who plays Harmony’s reformed gangster father Mac — face off one more time. Scenes in the Friars’ Club are a treat, especially some testy back-and-forth with Charles Grodin, and a roast featuring Cloris Leachman is the pinnacle of the film’s humor.

Harmony shares a sensibility with Jackie, and Mann is compelling in her delicately-wrought, if familiarly frantic performance. She’s the character in whom Jackie finds something to care about. But the arc of her character shows that the filmmakers didn’t know what to do with a complex woman like Harmony, despite her potential. She’s wacky, funny, angry, and just as off-kilter as he is, but she’s quickly set aside for Jackie’s journey to continue, and their combustible chemistry is squandered for stale and cliche plot developments that drag the whole thing down. The world of the “The Comedian” is rich, the themes often thought-provoking. But it eschews all that for a cutesy happy ending, one that Jackie definitely wouldn’t approve of.

MOVIE REVIEW

“The Comedian”

Grade: C+

Starring Robert De Niro, Leslie Mann and Danny DeVito. Directed by Taylor Hackford.

Rated R for crude sexual references and language throughout. Check listings for theaters. 1 hour, 59 minutes.

Bottom line: The cutesy ending undoes all the richness the film provides previously