When does art become propaganda? Does an image-taker capturing a politician in action become an inadvertent proponent of whatever message the pol delivers? Aurora Theatre explores this and other questions with the fearless, mutlimedia vehicle Leni, a two-actor performance by playwright Sarah Greenman. Drawing from real-life (and contradictory accounts) that filmmaker Leni Riefensthal gave about her work, the script has an older and younger Leni dialoguing — and wrestling with — their differing versions. Best of all, director Jon Tracy has cast Stacy Ross and Martha Brigham as the two Lenis; you won’t find more astonishing, right-on-the-edge-of-crazy-good actors in the Bay Area. Set design by Nina Hall should be wizardly, and likely will transform the 50-seat Harry’s UpStage black-box theater into a vestibule of visual assault and artistry.