After seeing Cynthia Erivo blow the roof off the theater in the Broadway production of “The Color Purple” in 2016, Debra Martin Chase was sure she’d found her Harriet Tubman.

Chase, the producer behind such movies as “The Princess Diaries” and “The Sisterhood of the Traveling Pants,” had been trying to make a film about the revered abolitionist for two years. When she saw Erivo as Celie onstage, she said to herself, “This is our Harriet.” She promptly arranged for a meeting.

A week later, when Erivo arrived at the Mandarin Oriental at Columbus Circle, Chase knew her instinct was right. ”She walked in, fabulous — short, blonde, natural hair,” she recalls. “Stylish and confident and dramatic.” The script needed work, but Chase asked Erivo to read it. Meanwhile, Chase called indie producer Daniela Taplin Lundberg (“Honey Boy,” “Beasts of No Nation”), for whom “Harriet” was also a passion project, to express her enthusiasm for Erivo playing the lead in the biopic.