For ‘Short Term 12’s’ John Gallagher Jr., a longer-range plan

NEW YORK — John Gallagher Jr. was at a media screening of his new movie “Short Term 12” a few weeks ago when a man came up to him with a critique of his series TV character, journalist Jim Harper of “The Newsroom.”

“You know, you’re a terrible embed,” the man told him, going on to list the ways Harper bungled his job as a reporter traveling with the Mitt Romney campaign in the second season of the HBO show.

It was hardly a comment from some idle observer: the naysayer was NBC News anchor Brian Williams.

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It’s perhaps a little incongruous that a high-school dropout and theater rat is being evaluated for his reporting bona fides by one of the most famous journalists in America. But it’s also a testament to the lived-in believability of his characters.

First in his stage work and now on the screen, Gallagher, 29, has honed an improbable acting career that centers on low-key likability more than showy emotional displays or other trappings of youthful performance. Though he’s different from many of his generation — he’s neither as tortured as some (think Ryan Gosling) or as strong and silent and others (think Channing Tatum) — Gallagher is slowly accumulating a roster of memorable characters, the kind whose surface sweetness conceals a more complex emotional life underneath (think a young Tom Hanks).

For years mainly a stage actor — he won a Tony Award in 2007 for his portrayal of Moritz Stiefel in the coming-of-age musical hit “Spring Awakening” — Gallagher has become a lot more well-known in the last 14 months as the emotionally bumbling producer of cable-news network ACN on “Newsroom,” whose second season has been airing this summer. Harper serves a key role on the series, not only because of his romantic travails — He’s with Maggie! With Maggie’s roommate! With Meryl Streep’s daughter! — but because he’s the rare voice of skepticism in the fictional news network’s zeal to report a military scandal.

For the last 10 days he’s been seen in Destin Daniel Cretton’s indie darling “Short Term 12,” which won top jury and audience prizes at SXSW before opening to strong reviews in Los Angeles last weekend. Starring as the group-home worker Mason, Gallagher has been able to add a new notch — as a generous and thoughtful foil to his girlfriend and co-worker Grace (Brie Larson), who is struggling with her abusive past.

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The real-life Gallagher comes off as similarly nice and down-to-earth — he suggests meeting at a restaurant near his apartment and orders a few beers, sitting at the bar unbothered — if also on the cautious side. (Pumped for on-set “Newsroom” scuttlebutt, he offers mainly that costar Alison Pill is a chain-smoker.)

Gallagher plays Mason with a fair degree of nuance. The character is sensitive but strong as the boyfriend, and hard-bitten but hardly jaded as a youth counselor. The movie avoids many of the cliches of the troubled-youth subgenre, and Gallagher’s performance is part of the reason why.

“It’s a character you don’t see very much, even in independent film,” he said. “Usually someone like that is just there to be supportive; he’s not given this rich history and life.”

Gallagher’s participation in the film nearly didn’t come off.

A few years ago, he had been depressed about not landing a part in what he describes as a big movie. “I was growing my beard, letting my hair go long, eating whatever I wanted. I think I gained about 15 pounds,” he said. Then Cretton called — saying, of all things, that he’d been looking for a man with a beard and slightly disheveled look. “The moral of the story is that you should get totally out of shape, and then the roles will come,” Gallagher said.

“Newsroom” had a similarly fragile back story. When Gallagher was offered the part in the show in the summer of 2011, he nearly turned it down because he had several months left on his contract in the Broadway production of “Jerusalem,” Jez Butterworth’s play about a group living largely off-the-grid in the British wilderness. He says he struggled for weeks with the idea of forsaking his commitment, eventually having the “intense” conversation with producers in which he told them he’d be leaving early.

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Theater is a world, it should be said, that the actor knows well. Growing up in Delaware, Gallagher would regularly take the train to New York to watch and eventually audition for plays. He landed his first gig when he was 15 in an off-Broadway show. He eventually parlayed that into bigger stage roles; his résumé also includes the Green Day musical “American Idiot” and “Farragut North,” the play on which the George Clooney big-screen drama “The Ides of March” is based.

Gallagher has lived in New York since he was a teenager, currently residing in a West Village building and flying to Los Angeles the last two springs to shoot “Newsroom.”

Though he plays educated, even erudite characters — Jim Harper is known for a deep knowledge of obscure policy issues — Gallagher himself never finished high school. (He says he’s thought on and off about getting a G.E.D. but hasn’t been moved to do so yet.) He’s been able to attract an audience thanks to a boy-next-door charm.

In fact, his Jim Harper character was initially more slick — think a wunderkind-ier version of Thomas Sadoski’s Don — but Gallagher says he read the part and believed he could bring more depth playing it sympathetically.

That doesn’t mean he’s beloved by those who watch the Aaron Sorkin show. Like many involved with “Newsroom,” Gallagher is regularly the object of social-media snark.

The actor, who says he has grappled with the question of how much social-media engagement to practice (he does it largely to promote side projects as a musician and songwriter), will nonetheless reply to comments about the plausibility of the show. He says he remains surprised by the passion — to wit, those who excoriated his character for giving up a key interview for the sake of a girl. He sometimes plays along, sometimes gently reminds Twitter dart-throwers that the show is fictional — and, oh yes, he didn’t write it. (He generally offers a kind of self-deprecating persona on Twitter. Sample Tweet: “Eating dinner alone. Both Sides Now is playing in the restaurant. Feeling lots of feelings.”)

For all the disdain “Newsroom” takes, Gallagher’s performance is rarely included in the targeting. Playing nice is harder than it looks, requiring an ability to generate compassion without sacrificing complexity.

It’s the kind of role Gallagher says he’s interested in continuing. He has begun shooting the lead love interest in the New York indie romance “The Heart Machine,” and is crossing his fingers for a “Newsroom” renewal. And then, with a kind of nice-guy shrug, he questions that direction. “It’s an actor-y thing to say,” he noted, “but I really don’t want to repeat myself.”

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