Earlier this year, the hit documentary “RBG” made clear how Supreme Court Justice Ruth Bader Ginsburg has come to be an enormously popular role model for women in their teens and 20s — and achieved pop culture celebrity to boot.

Now comes the Christmas release of “On the Basis of Sex,” which applies the Hollywood treatment to Justice Ginsburg’s beginnings as a smart but struggling lawyer who faced herculean challenges in her personal and professional life.

Director Mimi Leder and screenwriter Daniel Stiepleman (who is Ginsburg’s nephew) frame “On the Basis of Sex” as an underdog saga. And like a lot of underdogs in Hollywood movies, our heroine has a superpower that she must discover — and master — during her journey.

The movie is effective, and ultimately inspiring, in a way that doesn’t remotely challenge viewers other than to ask them to follow clever legal strategies.

The film opens in1956, during Ruth’s first days at Harvard Law School, where her husband, Marty, is in his second year. Immediately and repeatedly, Ruth (along with the viewer) is reminded of her second-class status as a woman in a man’s world.

It takes a while to reconcile the confident Justice Ginsburg of public record with the somewhat skittish character that British actress Felicity Jones creates. A wife, a mother and an aspiring professional, she’s patronized by everyone from the law school’s WASPy dean (a villainous Sam Waterston) to her husband (a stalwart Armie Hammer), and when she does stand up for herself, she risks being seen as a rabble-rouser.

Although the film neither conceals nor finesses Ruth and Marty’s Jewishness, it presents casual misogyny and an entrenched old boys’ network, not anti-Semitism, as the obstacles Ruth needs to navigate.

Consequently, she has to devise ways — both direct and elliptical — to raise the consciousness of her allies, including that of her devoted husband, before she can begin to challenge potential adversaries. While Marty certainly recognizes his wife’s brilliance, he’s a product of his upbringing and the times.

“On the Basis of Sex” devotes considerable screen time to the couple’s relationship, and for many viewers that will serve as the emotional heart of the film. Others will derive more pleasure from watching Ruth find her footing and her voice as a scholarly attorney, leaving Harvard after two years and going on to graduate from Columbia Law School.

As Stiepleman noted in an interview during a recent visit to San Francisco, “Coming out of law school, [Ruth] had three strikes against her: She was a woman, she was a mother and she was a Jew. Any one of those things alone, law firms would take the risk. It was the three together that made her unhireable in their eyes.”

Unable to find a job practicing law, Ruth takes a teaching position. Through a combination of determination, persistence and luck, however, she comes across a unique case that addresses the inequities of gender discrimination: The complainant, who looked after his mother but was denied the tax deduction for caregivers, is a man.

Earlier in the film, there’s a crucial chain of events that starts when Marty is diagnosed with cancer. Ruth not only takes care of him (and their small daughter) but also gets them both through law school. That experience as a caregiver gives her both the empathy and the understanding to identify with and persuade her would-be client, and to research and argue the case.

The lengthy courtroom scene that takes up the film’s final 20 minutes or so is genuinely effective and even emotional, despite the formulaic staging and the fact that we know Ruth will prevail. At the pivotal moment, we witness a character coming into her own, grasping her abilities and realizing her destiny.

And with that, the underdog becomes a superhero.

“On the Basis of Sex” opens Monday, Dec. 24 at Embarcadero Center Cinema in San Francisco and Friday, Jan. 11 at Shattuck Cinemas in Berkeley. (Rated PG-13, 120 minutes)