David Krumholtz, Oppenheimer’s Secret Weapon, Is Ready to Be a Little Less Secret

David Krumholtz had a secret. It was July, and it had been a few months since he ended his run in Leopoldstadt, the Tom Stoppard play that won four Tony Awards in June. SAG-AFTRA was about to go on strike, and Krumholtz would spend much of the rest of the summer on picket lines alongside the members of his union.

There were a lot of big things looming—but the biggest by far was Oppenheimer, the Christopher Nolan film that opened on July 21, one week after the actors strike began. Krumholtz’s role in the film had been announced during production, but, as he puts it, “I was on the cast list along with a lot of other wonderful actors. But I knew, Hey, I actually am in this thing quite a bit. And I knew that would surprise people.” So even as Oppenheimer’s premiere was cut short by the strike’s beginning, Krumholtz wasn’t feeling anxious—“because the anxiety that would’ve existed was replaced with, Oh, my secret’s out.”

Since Oppenheimer became one of the biggest movies in the world, people have told Krumholtz they’re glad to see him back—though to make it clear, he hasn’t gone anywhere. A professional actor since making his Broadway debut at the age of 13, and with an iconic role in the Santa Clause franchise, Krumholtz gladly calls himself a journeyman. “I’m very much a feather in the wind,” he says about his career bouncing from role to role. “For the longest time, I really didn’t love it. And now I put mustard on it and eat it.”

But Oppenheimer really does mark something different, a key supporting role in one of the year’s most successful and acclaimed films. Krumholtz plays Isidor Isaac Rabi, a physicist who befriended Robert Oppenheimer while they were both students, and functions in the film like the warm, avuncular conscience that Oppenheimer must ignore in order to push forward on building the atomic bomb. In one memorable scene, Cillian Murphy’s Oppenheimer invites Rabi to join the Manhattan Project in Los Alamos; Rabi initially rebuffs him, saying, “I don’t want the culmination of three centuries of physics to be a weapon of mass destruction.”

Cillian Murphy and David Krumholtz in Oppenheimer.

By Melinda Sue Gordon/Universal Pictures

Krumholtz swears he’s not being falsely modest when he says this: “Chris wanted Rabi to be one of the major hearts in the film, and he did a very, very specific and good job at making that happen. All I have to do is fill in the blanks and show up and be the guy.” But like so many other actors in the film, ingeniously cast by John Papsidera, Krumholtz’s existing persona lends so much to Rabi. Just as you might see Rami Malek in the background of an early scene and know with certainty he’ll be back in force later on, Krumholtz’s arrival promises wry humor and a quiet ferocity. It’s how, late in the film, he can send Josh Hartnett’s Ernest Lawrence scampering down a hallway with a single glare.

“I’m good at fooling people into thinking I’m smart,” Krumholtz says—there’s that modesty again. “You just kind of have to raise an eyebrow a lot.” From 2005 to 2010, for example, he played a crime-solving math genius on the CBS procedural Numb3rs, and earned a very specific fan: Christopher Nolan. Roughly 17 years ago, he says, Nolan “happened to be on the stage on the lot that I was working on, and he pulled me aside to tell me he was a fan of mine on the show Numb3rs.” Krumholtz has “learned the hard way” how that kind of chance encounter doesn’t usually lead to, say, being cast as the next Batman. “Certain people can just be fans and they have no idea if they want to work with you,” he says now. “And the same goes for Chris, except Chris remembered, which meant the world to me. I mean, it meant the world to me in any moment where it feels like my work mattered.”

Working since he was a child, Krumholtz learned the business and his craft as he went. It was Kevin Corrigan, for example, who taught him to embrace the uncertainty of a career in which he could receive a call telling him to hop on a flight to a set the next day. When he was about 20, a dear friend became “really, really famous”—no, he wouldn’t say who—and that friend’s experience “scared the living shit out of me.” So back to the journeyman career it was, a path that eventually led him to the HBO series The Deuce, where he learned to do something entirely new.

“Maggie Gyllenhaal taught me how to act,” he says plainly of his Deuce costar. “The way she taught me to approach our scenes together—to live in it.… Maggie just said, ‘Hey, no choices.’ She said, ‘I won’t make any choices if you don’t.’ And now to me, it’s the only way to do it. Watching my own work from before The Deuce, I could see myself playing towards the camera—indicating is the acting term for it. And I just wanted to stop doing that. I credit Maggie with giving me the confidence to do that.”

When the Oppenheimer audition came, Krumholtz had a sense that his career was slowing down; now, as an essential part of the odds-on favorite for the best-picture Oscar, the pace has changed entirely. Krumholtz attended the New York Film Critics Circle dinner earlier this month alongside Oppenheimer costars Benny Safdie and Dane DeHaan, all in support of Nolan’s best-director win. He’s learned not to live in expectation of what might come next, but also knows that his work is being seen, and that opportunities are likely to follow.

Then again, that Leopoldstadt experience means Broadway might call him back. That’s something he learned from yet another veteran actor with advice to share. “We were rehearsing in the same building as a play called the Piano Lesson,” Krumholtz says. “And Samuel L. Jackson was one floor up from us. And I would go out for a break outside on the street on 42nd Street there, and he’d be there also taking a break. One day I mustered up the courage to talk to him, and I said, ‘Hey, Sam, why do you do theater still?’ And he said, ‘I have to do it. I have to. It’s the real stuff.’”

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