Alden Ehrenreich, discovered by Spielberg in a bat mitzvah video, steals scenes in ‘Hail, Caesar!’

Ethan and Joel Coen’s 1950s-set showbiz comedy “Hail, Caesar!” is brought to life by a large, star-studded ensemble that includes George Clooney, Josh Brolin, Scarlett Johansson and Channing Tatum, but critics and audiences have zeroed in on the one major cast member without a household name.

As the hayseed movie cowboy turned romantic leading man Hobie Doyle, 26-year-old Alden Ehrenreich steals scenes with guileless charm, impeccable comic timing and an array of rope tricks.

In a rave review, Los Angeles Times film critic Kenneth Turan singled out Ehrenreich as “the best of the bunch,” while Matt Singer of ScreenCrush wrote that Ehrenreich “emerges as the film’s breakout star.” Though the well-reviewed film did only middling box office in its opening weekend, the young but experienced Ehrenreich is riding a whirlwind of industry attention.

On Sunday, two days after the movie’s release, Ehrenreich — who had just signed with a publicist for the first time — was reluctant to concede that his convincing simulation of a movie star might make him a movie star himself.

“I don’t know what it is that’s happening,” he said during an interview in the Beverly Grove area of L.A. “I think that’s yet to be decided.”

Not unlike Hobie Doyle, Ehrenreich in person has a warm and relaxed demeanor, seeming slightly dazed by his good fortune and protective of his ambitions. He said that he doesn’t get recognized and that “I have no idea what that would feel like. It’s one of those experiences that is so extraordinary that you can’t really picture it until it happens.”

Though he can have the brooding heartthrob appeal of a young Leonardo DiCaprio or Matt Damon, his first mainstream turn as a dramatic lead, in the supernatural teenage romance “Beautiful Creatures,” didn’t make major waves in its 2013 release. A 2014 Times article surveying Hollywood’s most promising young performers referred to Ehrenreich as “an intriguing question mark for now.”

The intrigue owes itself to Ehrenreich’s unusually auspicious training period, which found him performing in films by uncompromising auteurs like the Coppolas (Francis Ford and Sofia), Woody Allen, Park Chan-Wook and Warren Beatty.

He ascribes his illustrious résumé to something other than careful planning. “I think it’s just luck,” he said. “I would have loved to design it like that. These are my favorite filmmakers, you know? Getting to participate in that — and be included in that — is just crazy.”

The Pacific Palisades native was discovered by Steven Spielberg while performing in a friend’s bat mitzvah video, but he owes his debut role (and much else) to Francis Ford Coppola, who cast him as the young protagonist of his operatic, black-and-white 2009 family drama “Tetro” after a lengthy audition process.

“Tetro’s” intimate Buenos Aires shoot had a profound effect on the teenage Ehrenreich, and he thrived under Coppola’s guidance.

“That was everything I could have dreamt of,” he said. “Four months in Argentina, when I was still in high school. I was 18. Had never lived on my own before. And I’m in an apartment in Argentina by myself, going in to work with Francis every day … getting to pepper him with questions. It’s the craziest thing. It still makes me very happy to think about.”

Ehrenreich’s affinity for ambitious cinema came early. “My parents used to do these little film festivals in our house where we’d watch all the Marx Brothers movies, or Chaplin movies, and a lot of westerns.” While attending high school at Crossroads in Santa Monica, he combed the shelves of Vidiots’ directors’ section to discover a young actor’s New Hollywood starter kit: “The Godfather,” “Five Easy Pieces,” “Easy Rider” and “Midnight Cowboy.”

Though he had to do some research to play Hobie, a singing B-movie cowboy modeled after Gene Autry and Roy Rogers, Ehrenreich was a huge Coen brothers fan long before they tapped him to play his first comic role. “Hail, Caesar!” may feel like an exuberant lark compared with the Coens’ previous Tinseltown fable “Barton Fink,” but Ehrenreich sees it as another ambitious comedy of ideas.

“They’re able to make fun of things and express love for them at the same time,” he said. “They’re able to get in big questions and issues and themes because the movies are so funny. There’s a Billy Wilder quote: ‘If you want to tell an audience the truth, make them laugh or they’ll kill you.’ ”

The Coens are generally skeptical of heroism, but despite his outward silliness, Hobie is the latest in their long line of principled, quietly wise cowboy figures, a brotherhood that includes Sam Elliott in “The Big Lebowski” and Tommy Lee Jones in “No Country for Old Men.”

“They have an ear for the way people really talk,” he said. “No matter how zany the characters are, they’re absolutely rooted in a logic and an understanding of how a character like that would really behave, think or talk. It’s never just a caricature.”

As Ehrenreich prepared to fly to Germany, where “Hail, Caesar!” will open the Berlin Film Festival, he seemed grateful for the slightly delayed arrival of the Hollywood spotlight. “If I had to do a lot of promotion as a kid, it would have been very intense,” he said. “I’m really glad I got to go through high school, have a college experience and have the last five years since then, just … being a person.

“And it’s happening in my hometown, which makes it easier. The people I see every day have known me since I was a little fat kid.”

calendar@latimes.com