– Heart-tugging drama is usually not effective in a studio screening room, where the smell of executives’ sweat is more likely to waft through the aisles than overly buttered popcorn. But as the lights went up following an advanced episode of “This Is Us” this month, a serious case of the sniffles had spread across the VIP audience, which included cast member Chrissy Metz.

“Forget crying. I was sobbing,” said Metz, who plays a Steelers fanatic tackling weight issues, still dabbing away tears 20 minutes later at an after-party on the Universal Studios lot. The show’s nearly 15 million viewers can relate. They’ve made the NBC drama the most watched new show of the season and the most unexpected rookie hit since “Lost” more than a decade ago.

The show, which traces a racially diverse family’s sentimental journey over the course of four decades, is the beneficiary of an enviable time slot, a savvy marketing strategy and solid reviews. But it owes the bulk of its success to timing. With an increase in political uncertainty and rising racial tensions, America needed an escape hatch.

“I think people were hungry for this kind of entertainment,” said actress Mandy Moore, who in one recent episode goes into an emotional tailspin when she forgets her husband’s birthday and waddles her very pregnant body down to the liquor store to assemble the world’s unhealthiest yet irresistible cupcake. “In this chaotic, unknown moment we find ourselves careening toward, I think people want cathartic entertainment that touches them.”

“This Is Us” breaks many rules: Jumping back and forth in time, leaving major characters on the sidelines for entire episodes, making time for long, uninterrupted monologues that a short-attention-span audience isn’t supposed to sit still for.

Its boldest departure? No villains. Even the father who re-emerges decades after abandoning his infant son on the fire station steps has mellowed into Mr. Rogers, albeit one with a secret gay relationship and a terminal disease.

“We’ve seen a lot of stuff lately about the evil people do to each other,” said Gerald McRaney, who has appeared several times on the series as a doctor with impeccable bedside manners. “I think people are tired of feeling cynical about life. People want to be reminded of the goodness that’s in us. It’s time to bring that back, maybe.”

But TV has never had much success with bawl-in-the-family drama. To find a show with the same emotional pull — and success — of “This Is Us,” one has to go back to “Little House on the Prairie” and “The Waltons,” both of which were off the air by 1982.

Tear-jerkers have also dried up at the cinema. Films with the same DNA as “Terms of Endearment,” “Kramer vs. Kramer” and “Ordinary People,” all Oscar winners, tend to get quieter releases or go straight to Netflix.

“As filmmaking gets more advanced, we tend to reward art that’s a little more withholding,” said “This Is Us” creator Dan Fogelman, whose 2012 cinematic release “The Guilt Trip,” a love letter to his mother starring Barbra Streisand and Seth Rogen, tanked. “Maybe sentiment has become a loaded word and everyone’s scared of it.”

That attitude may explain why Fox passed on airing “This Is Us,” which is a 20th Century Fox production — opting instead to sell the project to NBC, home to “Parenthood” and “Friday Night Lights.” Both of these family-focused series managed to stay on the air for at least five seasons, despite always living on the brink of cancellation. (“Friday Night Lights” would eventually premiere its episodes on DirecTV’s 101 network.)

“It’s going to be a lucrative, important show for us and will live in our library for the rest of time,” said Gary Newman, CEO of the Fox Television Group.

Blockbuster territory

The first sign that NBC may have struck oil was back in May, when a trailer for its upcoming drama was made available to the public. Within 11 days, nearly 80 million people had viewed it online, a mind-blowing number when you consider that it took the first official trailer for “Star Wars: The Force Awakens” almost two months to reach that same mark.

“Those are staggering totals that not only dwarf any new series trailer,” reporter Nellie Andreeva wrote for Deadline.com last summer. “They put the low-key ensemble dramedy with no famous title, mega stars or special effects into blockbuster movie territory.”

For the second week in January, “This Is Us” finished sixth among total viewers, behind only NFL playoff games and CBS’ long-running cop drama “Blue Bloods.” It is nearly as popular as AMC’s “The Walking Dead,” the biggest success in cable history.

“Zombies are cool. I like zombies,” said “This Is Us” cast favorite Milo Ventimiglia, taking on the role of a father who, aside from growing a porn-star mustache, appears to make every right decision. “But not everybody can be a superhero. Not everybody can be involved in a scandal. Not everyone is living in medieval times. Going up against premium cable TV is tough, but it doesn’t mean you can’t have a beautiful story that doesn’t have the excess of shock.”

Response from fans has been overwhelming, said Ventimiglia, who seems particularly pumped to have heard from his high school drama teacher. She told him that despite his previous success in “Gilmore Girls” and “Heroes,” his latest project has brought her the most satisfaction.

Susan Kelechi Watson, who plays a no-nonsense mother, said she’s gotten hugs from a wide range of fans, from 11-year-olds to people in their 50s who got turned on to the program by their parents.

“A lot of people have told me they have a group that discusses the show the next day,” she said.

She predicted that her drama’s surprise success will influence future network decisions.

“I think it will open up a pathway,” she said. “Shows that have an impact usually do.”

Proceeding with confidence

Copycat shows are almost certain to pepper the 2017-18 lineup, in much the same way shows about 20-somethings gabbing in coffee shops emerged on the heels of “Friends.”

But former NBC Entertainment Chairman Warren Littlefield has advice for any executive who thinks the runaway success of “This Is Us” is based solely on its family-first formula.

“It’s a reminder that you don’t need traditional franchises to be successful, that it doesn’t have to be about a doctor, or a lawyer or a cop,” said Littlefield, an executive producer on FX’s “Fargo.” “But the show works because of Dan Fogelman’s vision, his sense of storytelling and his deeply emotional, enormous heart. Audiences embraced it because it’s fresh territory.”

One group that hasn’t gone gaga over the series is critics. The show failed to win any Golden Globes this month, despite three nominations. Yes, the show has gotten largely positive reviews — Rotten Tomatoes gives it an 89 percent approval rating — but the show finished only 12th in Uproxx’s annual poll of TV critics, just behind Sundance’s “Rectify” and AMC’s “Halt and Catch Fire.”

“It’s not that we hate it,” said Daniel Fienberg, a writer for the Hollywood Reporter and vice president of the TV Critics Association. “But we’re predisposed, at least somewhat, to favor the prestige cable shows we’re accustomed to.”

The more pragmatic critics will have time to come around. NBC has renewed the show for two more seasons, a rare display of confidence for a rookie show.

Fogelman seems braced for the inevitable backlash from those who think the show will quickly run out of steam — and tears.

“We know where the series is going and how we’re going to keep people on their toes,” he said. “I feel really confident.”