By a strange quirk of coincidence, Spike Lee’s “BlacKkKlansman” is the second film this summer in which an African-American man uses a “white” voice on the telephone to jump-start his career.

The first was Boots Riley’s acclaimed satire “Sorry to Bother You,” which exists in an alternate reality.

The other film is based on fact.

“BlackKklansman” (opening Friday in Chicago) is the story of Ron Stallworth, the first black detective in the Colorado Springs Police Dept., who in the early 1970s infiltrated the Ku Klux Klan by affecting a white, racist, anti-Semitic character. (For face-to-face meetings, Ron’s white partner would take over the role, using information provided to him by Ron.)

John David Washington plays Stallworth. For Washington, 34, a former college football star and pro prospect best known in show business for HBO’s “Ballers,” technically this isn’t his first role in a Spike Lee film. When Washington was 8, he had a single line in “Malcolm X” (the line was, “I am Malcolm X”) in the film that starred his father, Denzel.

John David (“You can call me JD”) Washington was in Chicago recently to talk about “BlacKkKlansman.” I suggested we meet in Grant Park, near the Gen. John Logan Memorial — a gathering point for protesters in the 1960s and 1970s. On a crystal-clear summer morning, we took a walk and discussed the film.

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Washington was working on the Robert Redford-starring film “The Old Man & the Gun” (coming in September) when he got a text from Spike Lee.

“He said, ‘Where are you? I’m going to send you this book [by Ron Stallworth] to you,’ ” says Washington. “I read the book and I said, ‘So I’ll be a Black Panther or something like that?’ And he said, ‘No, you’re going to be the detective.’

“There wasn’t any discussion about ‘Are you interested?’ or, ‘Would you like to see a script?’ It was, ‘You’re doing this.’ And now I’m a different, better actor because of this.”

The real Ron Stallworth was born in Chicago but grew up in El Paso, Texas. He joined the Colorado Springs Police Dept. in the 1970s and infiltrated the Klan by posing as an eager recruit on the telephone. Washington’s first meeting with Stallworth was at a table read of the script.

“My goodness, he was just great and generous with his time. He passed around his Ku Klux Klan membership card. We saw it, we held it. It gave me the chills. It made it more real. He’s such an intense guy; he was all about the mission.”

The movie is set in the 1970s, and as is the case with nearly all of Lee’s films, music plays an integral role.

“My playlist consisted of nothing but late ’60s and early ’70s,” says Washington. “I was going to bed every night with ‘Soul Train’ and the soundtrack to ‘Superfly.’ I’d wake up to Curtis Mayfield.

“It was a very radical, expressive time. The pop culture, the Afros, the music. All this intense stuff like Vietnam was going on, but [young people] were still having a good time, too. Spike is a master of incorporating that into his films. I mean, even with [serious subject matter], we’re still talking about people going to Friday night at the movies.”

There’s also plenty of humor in the story — often at the expense of the buffoonish (albeit dangerous and hateful) Klan members.

“We played it as true and organically as possible,” says Washington. “I never felt we were playing anything for laughs. What I find interesting is to see the film with audiences and hearing what they find funny. Some [of what happens] IS ridiculous.”

Ron is undercover (on a different assignment) when he meets and falls for a student activist played by Laura Harrier. She thinks he’s a civilian and wouldn’t give him the time of day if she knew he was a cop. In a way, Ron is never telling the truth. Neither the targets of his investigation nor the object of his affection knows his real identity.

John David Washington stars with Laura Harrier in "BlacKkKlansman."

John David Washington stars with Laura Harrier in “BlacKkKlansman.” | FOCUS FEATURES

“An African-American cop — are you woke? Are you all about the law?” says Washington. “Ron Stallworth says you can change things from the inside. He’s actually using the law, and it’s very American because he’s trying to do things the right way. As Ron says, ‘Just because I’m not wearing a black beret doesn’t mean I’m not for the liberation of my people.’

“And Ron was supported by his white colleagues in the department. That’s an important takeaway for people to see too.”

The ensemble cast of “BlacKkKlansman” also includes Adam Driver as Stallworth’s partner, Flip Zimmerman, who is Jewish but has to spew the most hateful anti-Semitic views when he’s undercover as a KKK recruit, and Topher Grace as the young and thoroughly despicable David Duke, the national leader of the Klan.

“Adam is so talented, such a professional,” says Washington.

“He made me bring my A game — everybody on the cast was like that. There was such team chemistry, it was motivating to get in the ring with all these people, like Laura and obviously what Topher did.

“Coming from a football background, when everybody is doing their job and operating on such a high level, it only motivates you to do the same.”

Our walk reaches a dead end due to construction, because after all, this is Chicago in the summer, and where can you walk for more than a few blocks without running into construction? We turn around and head back to our original meeting place.

John David Washington has mentioned football. (He starred for Morehouse College and played on the practice squad of the then-St. Louis Rams and in NFL Europe before turning to acting.) I ask him if he picked that particular sport because the helmet affords more anonymity than one would have playing baseball and basketball.

“Yes, but I stopped growing, too,” he says. “I couldn’t be an [NBA] center. But yes, I felt like I could hide a little bit, hide from certain people I was related to.

“I was just that Washington kid. There are a lot of Washingtons that have played football. I could just blend in more and carve out my own name quietly. It was a healthy, positive thing.”