Spanning several decades (and burying the leads under makeup before it’s over), the film begins with Tammy and Jim meeting in 1960 and follows them into the ’90s. The pair initially embark on a whirlwind romance, built around the desire to preach the gospel and make a killing doing it. “God does not want us to be poor,” a young Jim says, raising the eyebrows of his Bible teacher.Within a few years, they discover television, taking a job working for Pat Robertson’s Christian broadcasting operation, with Jim spouting the word and Tammy beguiling kids with puppets and song.Tammy’s approach to religion welcomes everyone, which puts her at odds with Jerry Falwell Sr. (Vincent D’Onofrio), who not only winces at a woman entering the conversation but seeks to build the religious right’s political power through condemnation of gays.”We paid for all this,” the couple marvels upon seeing Robertson’s palatial estate, before the Bakkers launch their own broadcasting empire, the Praise The Lord network (PTL), funneling money into their lavish lifestyle almost as fast as their viewers (or “partners,” as Jim calls them) can phone in contributions.Adapted from the 2000 documentary of the same name by director Michael Showalter (“The Big Sick”) and writer Abe Sylvia, the movie bounces along fitfully through the flush years, exposing strains in the relationship as Tammy eventually turns to pills, washing them down with Diet Coke.Questions persist, meanwhile, about PTL’s shady finances, with Jim using what he dismisses as being “persecuted by the secular press” as another means of separating the flock from their money.Currently in HBO’s “Scenes From a Marriage,” Chastain remarkably manages to transform into Tammy Faye — from the chirpy voice to the cartoon eyelashes — and still get beyond mere impersonation. As for supporting players, few register except for Tammy’s skeptical mother (Cherry Jones), who has the good sense to keep asking how her daughter can pay for those fabulous frocks and lakefront home. While Showalter punctuates the movie with actual news clips and deftly recreates the Bakkers’ surreal “Nightline” interview, the malfeasance happening within PTL is handled vaguely. Jim snaps at Tammy as he obsesses over his various deals, but by sympathetically keeping the focus on seeing through her eyes the narrative becomes messy, leaving blind spots about the network’s inner workings before it all comes crashing down.In one respect “Eyes of Tammy Faye” feels inordinately timely, with Falwell discussing the power of budding conservative media offsetting voices on the left, and the Bakkers encouraging their audience to trust them and tune out critics.Like the documentary, “The Eyes of Tammy Faye” highlights contradictions and complexity surrounding its title character largely overlooked at the time, from daring to compassionately interview someone with AIDS (prompting a rebuke from Falwell) to the misogynistic treatment she faced both within the faith community and from the media.It’s a terrific performance — laying on all that makeup only to dig through it and find the woman within. But it comes in the service of a movie that doesn’t measure up to it. “The Eyes of Tammy Faye” premieres in US theaters on Sept. 17. It’s rated PG-13.