Margot Robbie gives an incisive performance as Olympic figure skater Tonya Harding. (NEON/NEON/30WEST)

With its title tongue-in-cheekily evoking "I, Claudius," another epic tale of madness and debauchery, the dramatic comedy "I, Tonya" revisits — with verve, intelligence, scathing humor and more than a touch of sadness — the bizarre 1994 attack on figure skater Nancy Kerrigan by goons associated with the camp of Kerrigan's athletic rival, Tonya Harding. If dredging up that tawdry subject all these years later seems tabloid-worthy, and little else, you should also know that the movie is a meditation on the elusiveness of truth. (The title also evokes a witness taking an oath.) In addition to all that, it's a portrait of an America at the dawn of the 24-hour news cycle, the coming epidemic of not-my-fault-ism and our soon-to-be-pathological fixation with fame-for-fame's-sake.

"I, Tonya" is funny when it wants to be, poignant when it needs to be and surprisingly effective in harnessing these deeper themes to a character who might otherwise be dismissed as a lightweight laughingstock. "Generally people either love Tonya or are not big fans," says the skater's first coach (played by Julianne Nicholson), in an early voice-over that signals the film's intentions to paint Harding as a national icon, for better or for worse. "Like people either love America or are not big fans. Tonya was totally American."

Directed by Craig Gillespie from a screenplay by Steve Rogers, the film is based on what we are told, via on-screen titles, were a series of "irony-free, wildly contradictory, totally true" interviews that Rogers conducted with Harding and her ex-husband Jeff Gillooly (masterfully rendered here by Margot Robbie and Sebastian Stan, in period-perfect makeup, hair and clothes). It begins with 4-year-old Tonya's arrival on the ice, pushed there by her stage-mother-from-hell, LaVona Golden (Allison Janney, puffing on More cigarettes and swearing like a longshoreman). From that point forward, Gillespie tracks Tonya's slippery path, from the skater's abusive childhood to her downfall while still in her 20s.

Robbie's performance is a marvel of a disappearing act, with the Australian actress transforming herself beneath a veneer of tough-girl makeup, crunchy hair spray and the Oregon-born skater's flat Pacific Northwest accent. But the role is more than an impersonation, and Robbie is able to find — and to show us — the broken pieces of Tonya's damaged soul, with a kind of fierce vulnerability that makes her not just sympathetic but, at times, heartbreaking. Stan is also very good as Jeff, a schlemiel whose account of the events he is said to have masterminded often flies in the face of Tonya's version of the same things.

Present-day reminiscences by these two characters frame "I, Tonya," which plays out as a series of flashbacks, during which Robbie occasionally breaks character to directly address the camera. The supporting cast is impeccable, most notably Bobby Cannavale as a TV producer from the tabloid news show "Hard Copy," and Paul Walter Hauser as Gillooly's imbecilic co-conspirator Shawn Eckhardt.

But it is Janney who steals every scene she's in, as LaVona, a harridan whose noodging goes well beyond tough love. At one point, LaVona throws a paring knife into her daughter's arm. In another, she bribes a spectator at one of Tonya's competitions to heckle the young athlete, believing that her daughter will skate better if she is under pressure. In an extreme example of this psychological torture, a very young Tonya is forced to urinate on the ice after her mother won't let her take a bathroom break. "Skate wet," LaVona tells her, coldly.

If such scenes sound shocking, they are. But the film softens the bouts of cruelty with an abiding sense of humane, if absurdist, comedy, smoothing out the tonal shifts that may have you gasping in horror one minute and laughing the next.

Most intriguingly, Kerrigan (Caitlin Carver) appears in the film almost not at all. "I, Tonya" suggests that, in some ways, it's Tonya who is the victim. At the same time, it doesn't offer any excuses or pull its punches. Tonya Harding is no angel, as the film makes clear, but we're also reminded of her grit, determination and accomplishments: The skater was the first American woman to execute a triple axel, in 1991. "I Tonya" argues that it is not Kerrigan, but this little hellion, who first takes the ice to the tune of Cliff Richard's "Devil Woman" who may be — not despite, but because of her unsavory qualities — America's real sweetheart.

R. At area theaters. Contains pervasive crude language, violence and some sexuality and nudity. 120 minutes.