With every part, Patricia Clarkson exudes an elegance and charm that likely emanates in some measure from her New Orleans upbringing. Often, though, the actress doesn’t get the chance to play a Southerner. A new film, “Lilly,” remedies this by featuring Ms. Clarkson as Lilly Ledbetter, the Alabamian equal pay activist, and her performance not only feels authentic and lived-in but is also one of her best. 

Ms. Clarkson portrays a 30-year period starting with when Lilly was initially hired in 1979 to work at a Goodyear plant in Gadsden, Alabama, and running until her tireless efforts lead to President Obama signing the Lilly Ledbetter Fair Pay Act in 2009. Compressing public and private events in an effort to gin up tension, the independent feature is deeply conventional, pumping up the inspirational music as it hits predictable dramatic beats. It’s also ineptly edited at times, though Ms. Clarkson proves compelling throughout.

Surprisingly, the film is also somewhat of a based-on-a-true-story/documentary hybrid, involving as it does a considerable amount of contemporaneous news clips and interviews with a Supreme Court justice, Ruth Bader Ginsburg, who’s now deceased. After Lilly loses her case against Goodyear in the high court, it’s Ginsburg’s oral dissent that drives Congress to address a statute of limitations issue in the Civil Rights Act of 1964.

Initial scenes show how Lilly endured harassment while learning each step in the tire-producing process in order to secure a supervisor position during a period of management diversification. By 1989, Lilly had become an area manager and she witnesses the near-rape of a female co-worker by male employees, filing a report on the victim’s behalf. While watching these scenes viewers might be reminded of another feminist film inspired by true events, 2005’s “North Country” starring Charlize Theron, though hearing Ginsburg discuss the difficulties women experience in a workplace dominated by men gives them, depending on your state of mind, an extra charge or a layer of redundancy.  

We also hear Ginsburg mention “work-life balance,” and the film explores Lilly’s personal life as well. John Benjamin Hickey plays Charles, Lilly’s husband and a career Marine, and the tender, comfortable chemistry between the actor and Ms. Clarkson is the most engaging dynamic of the drama. Because we know how the story of Lilly’s fight for equal pay turns out, it’s Lilly and Charles’s relationship and their responses to various difficulties, including her decision to sue Goodyear and his cancer, that provide a current of uncertainty and much of its emotional heft. Indeed, Ms. Clarkson and Mr. Hickey demonstrate such genuine mutual affection that one hopes writer/director Rachel Feldman or another filmmaker pens a romantic comedy for the pair to star in.

Lilly’s decision to sue her employer occurs after she’s injured on the factory floor after being demoted, despite acknowledgements that she’s a top-performing manager. With the film now in full color mode to denote her newfound determination, she tells several lawyers at a Birmingham firm about the years of workplace harassment and depreciation. One senior partner asks why she stayed for so long, adding, “Certainly no amount of money is worth your health and safety?” 

Ms. Clarkson as Lilly takes a small pause before replying, “I haven’t had the privilege to see it that way.” It’s a riveting reminder of unconscious class bias and the limited opportunities available in many rural areas and small towns. This is followed up with Lilly recounting how a doctor once suggested she have a hysterectomy as part of a study in order to pay for a medical procedure for her son, and the point becomes even more pointed. 

An anonymous tip informs Lilly of how she was being paid significantly less than male managers, and it is on this pay inequality charge — not sex and age discrimination — that she wins her first trial in 2003. Yet she loses Goodyear’s appeal, leading to her lawyer Jon Goldfarb (a solid, empathetic Thomas Sadoski) to encourage her to take the case to the Supreme Court. After the loss, Ms. Feldman highlights how Lilly glad-handed with politicians from both sides of the aisle to get the law changed, espousing the belief that gender equality shouldn’t have a political affiliation. There’s also a clever scene illustrating the shamelessness of politics: During the 2008 presidential campaign, representatives from the Obama and Hillary Clinton campaigns knock on her door at the same time.  

While Lilly considered herself apolitical, Ms. Feldman includes glimpses of unprincipled corporate practices, backroom-deal lobbying, a slimy conservative politician, and even intimidation. Near the end, as Congress is close to voting on the bill in 2009, we see Lilly confront a Chamber of Commerce official. She acknowledges that supporting business is important, but she also admonishes him to “think about the future.” This future appears in the film’s final scene, when several young restaurant waitstaff — both men and women — honor her after the law is passed. Lilly Ledbetter may have died last year, yet “Lilly” depicts with grace and grit how her message of equal rights lives on.