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“Hamilton,” the blockbuster musical, has wowed a president, celebrities and anyone with a patriotic pulse. We went backstage with one of the stage managers.

It was Amber White’s second day as a stage manager on “Hamilton,” and Lin-Manuel Miranda, the show’s creator and star, was sick.

Viewers who buy their tickets months in advance are never happy to hear about a substitution. This was Broadway’s hottest show, based on a brick of a book by historian Ron Chernow, a fresh depiction of the New Yorker who fathered the American banking system, endured a sex scandal, and died in a duel. This was the first time that Miranda or Javier Muñoz, who plays the role on Sundays, didn’t appear as the title character. The role went to Jon Rua, the understudy, making his debut as America’s ten-dollar founding father.

White and the production team called an emergency rehearsal — 30 minutes long — for which the cast came to the theater. And then the show went on: “flawlessly,” White said, thanks to Rua but also the professionalism of the rest of the cast and crew.

White, 36, is one of the crew members in the room where it happens for eight shows a week, critical to the musical’s success but largely unseen.

Right-hand men and women

Stage managers, three of whom work at a time on “Hamilton,” are the guardians and protectors of the show and the cast — “a cross between a flight attendant and a mom,” White says — who tend to the mental and psychological well-being of the actors.

They are also often with the show long-term, from pre-production meetings on design and concept through to rehearsals, previews and performances, taking care of the practicalities of scheduling and organization. And, always, troubleshooting.

During a recent production of “Hamilton,” an ensemble member hurt his neck with about 35 minutes left in the show.

Coming off stage, squeezing past barrels of prop rifles and shelves of neatly stored mugs, he went to the stage managers’ office to find White. The actor said he couldn’t go back on.

Quickly, White paged one of the swings — an understudy ready to fill in for multiple roles at a moment’s notice — upstairs in his dressing room. She and the other stage managers coordinated the switch, getting the swing into costume and microphone and on stage in time for his new character’s next appearance. The hurt actor went home.

The show went on. The audience never noticed. Crisis averted.

The other part of the stage manager’s job is “preserving the artistic integrity” of the show, White says. The original director and choreographer check in from time to time once the show gets rolling, but on “Hamilton” the stage managers and a small creative team make sure the show stays consistent.

“You’re supposed to do the exact same thing every day, but the show is a living, breathing thing,” says White, in which even an actor’s interpretation of character might evolve. Sometime it evolves too much, and the actors have to tone down their performances.

It’s not surprising that the tension builds for the actors. In this show, “you’re at war so often,” White says.

History has its eyes on you

White has been a stage manager since college, when she switched from finance to a theater major.

After working in regional theater and in California, she came to New York with “two suitcases” and got her break on “Avenue Q.” She met her husband at the Broadway Show Bowling League — he’s a stagehand on “Kinky Boots.” They’ve never worked on a show together. Both count themselves lucky to be in stable jobs on Broadway for the moment. It’s not the kind of business where you “get an office job and sit in it for 20 years,” White says.

The “Hamilton” phenomenon is a “once in a lifetime” experience, particularly for the young actors making their first appearances on Broadway, says White.

Hundreds of fans wait on the street outside the theater before the show in a bid for lottery tickets. Miranda, who is both the show’s lead and creator, used to do a short live skit to entertain the show’s fans while they waited, but had to discontinue it for safety reasons, White says. Since then, Miranda has brought the mini-shows, known as Ham4Ham, online.

Backstage, the actors and crew can escape the mania. There’s not much more room than in a typical Lower East Side walkthrough, and the stage managers’ office is prime privacy real estate. It also has the only stage-level bathroom, so celebrities are often stored there after performances — yes, President Barack Obama, too.

Before the show, one of the stage managers makes his or her way to the crow’s nest, stage-left, reachable by a ladder. This is called the jump, and it’s from this hidden perch that one of the stage managers calls and manages the play — checking the building’s temperature, overseeing entrances, cueing the enormous bank of lights, unseeable from the audience but working busily from above.

“No matter how big a hit outside, we’re still doing the same job.” When the curtain’s up, “the noise goes away,” says White.

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