Peggy Sirota for Variety

Pete Davidson could have played Donald Trump on “Saturday Night Live.” In 2015, the NBC sketch show asked him — along with every other male cast member — to audition for the part of the Republican underdog, who was clearly running for president as a joke. “It was bad,” recalls Davidson on a recent walk through downtown New York. “First of all, I’m 10 pounds, so I looked insane. They made us all get dressed up and tanned up. I sounded like Thunderlips from ‘Rocky III.’” He re-creates a hissing voice reminiscent of a villain on a morning cartoon. “It was a nightmare. If I could get my hands on this tape, it’s embarrassing as f—.”

His missed opportunity meant another job for Alec Baldwin, but Davidson doesn’t need to despair. In the last four years, the 24-year-old has steadily become one of the show’s most valuable — if sometimes underused — players. You can catch him as the straight man in skits, such as a customer in a diner who orders lobster, prompting the crustacean to beg for his survival by belting out the soundtrack to “Les Misérables.”

On the Weekend Update segments, Davidson found his voice. Every few weeks, he sits at the anchor’s desk next to Colin Jost or Michael Che and delivers a three-minute take on the news, interspersed with comments about his penis. “I’ll rant, and I listen to it and pick the best chunks,” he says. “They’ll be like, ‘Cool, use that.’” These meditations have become some of the most popular “SNL” clips on YouTube. “He has real support in the audience,” says executive producer Lorne Michaels. “People love him.”

Even more now, because Davidson’s public persona has exploded since his engagement to Ariana Grande in June after only a few weeks of dating. He’s inspired a popular meme (“big dick energy”) and won the internet’s vote of approval for cutest couple, after taking her to the VMAs and sprinting past the D-list celebrities from the reboot of “The Hills.” Davidson met Grande on the set of “SNL” when she hosted in March 2016. “I was obviously ogling and trying not to be creepy,” he says. They didn’t start officially seeing each other until last May. “We didn’t know another person could feel — or treat a person — like that.”

The destination of our walk today is the apartment in Chelsea that Davidson shares with Grande. “I didn’t want to do something corny,” he says about the way he proposed. “We were in bed hanging, after watching a movie. I was like, ‘Will you marry me?’ It was really dope.” He wasn’t sure if she’d say yes. “I’m still convinced she’s blind or hit her head really hard,” he says, laughing. “Something is going to happen, and she’s going to be like, ‘What the f— is this thing doing around?’ For right now, it’s rocking.”

Like many comedians, Davidson mines his material from dark times in his life. When he was 7, he lost his dad, Scott, a firefighter from Staten Island, in the 9/11 attacks. He struggled to fit in and contemplated suicide. In high school, Pete found out he had Crohn’s disease, which he says led to chronic marijuana use for relief. After two stints in rehab for pot, he was diagnosed with borderline personality disorder. He says that with new medication, he’s stable (and smoking again). “The last few years have been real rough with me,” he says. “I took all these mental health classes and really spent a lot of time getting me good.”

On TV, Davidson’s wry timing and syncopated delivery have drawn comparisons to Adam Sandler. He’s not so sure, though, that he’s cut out for stardom. “The movie business is really hard,” he says. “I don’t want to do that many movies. I would like to do a handful over a period of time.” He’s now filming a part in the drama “Big Time Adolescence,” which is why he bleached his hair. He and his writing partner Dave Sirus have sold two scripts, which have yet to be made, and they are working on a third.

Davidson tells a story about how over the summer he had a chance to meet one of his idols. “My favorite person is Jack Nicholson,” he says. “Lorne invited me to dinner with him.” Even though it broke his heart, he decided not to go. “I didn’t want to f— it up,” he says. “I’m a dork. I would rather Jack Nicholson not know I exist than try to be his pal. I feel like I saved myself.” He envisioned all the ways he could let Nicholson down. “It’s a nice restaurant. I come in a Spider-Man T-shirt. My vibe is very different.”

As a teenager, Davidson performed at a bowling alley that doubled as a comedy club called the Looney Bin. His set was intensely personal, drawing from his life. That led to parts in TV shows and films. After “Trainwreck,” in which he portrayed a hospital patient, his co-star Bill Hader recommended him to “SNL” for an audition. Michaels says he wasn’t put off by Davidson’s lack of interest in sketch comedy, pointing out that Gilda Radner once told him that she didn’t do characters. “And what she’s famous for are characters,” Michaels says. “I think most people don’t know what they can do until they try it.”

When he started at “SNL” at 20, as the fourth-youngest comedian in the show’s history, Davidson thought he’d maybe survive a season. “I’d assumed I’m going to get fired and I’d have this credit,” he says. Davidson doesn’t like to watch himself on TV. And he doesn’t mind that you don’t remember some of his skits, such as his parody of Marco Rubio. “It’s not going well with me and impersonations,” he says. “That s— is a whole ’nother sport.”

“I’m able to do stand-up and fuck around because hopefully the worst thing that has ever happened to me happened.”

Life at 30 Rockefeller Center took some adjustment. He says he hasn’t turned on his computer at work once in five years, and he was bummed when his sketches were cut. “Everybody there is an adult,” he says. He recalls when Trump hosted the show before the Republican primaries. “It wasn’t the most fun week ever,” Davidson says. “He doesn’t get jokes. He doesn’t get tone. He doesn’t get punch lines. He’ll say words differently. He’s just a dweeb.”

Davidson thinks about it. “Dude, any president that is taking pictures of himself on a private plane eating Kentucky Fried Chicken is a f—ing psycho,” he says. “What are you? A f—ing Kardashian?”

Davidson is so chill that he offers me a hit off his joint. He has more than 50 tattoos — at least he thinks so; he hasn’t counted them all — including one of Hillary Clinton on his leg. “I got the tattoo after she lost the election because she’s such a cool person,” he explains. His other reference points, such as “Mrs. Doubtfire” and “Big Daddy,” are mostly from the ’90s. Movies were an escape for him. “If my dad didn’t die, I wouldn’t be a comic,” he says. “I’d be a construction worker in Staten Island or a basketball coach.”

That tragedy changed his outlook. “I learned what death was,” Davidson says. “And you’re not really supposed to learn about that until high school, when one of your friends falls asleep in the garage, or whatever,” he says, not resisting the urge to squeeze in a funny line. “To learn how anything can just be taken away from you early gave me this sense of ‘F— it. Whatever, dude.’ I’m able to do stand-up and f— around because hopefully the worst thing that has ever happened to me happened.”

He spent most of his life trying to conquer his demons. “I’ve been in and out of mental health facilities since I was 9,” he says. “I tried to drown myself in the pool when I was in the fourth or fifth grade. I was trying to get my head stuck in the ladder in the deep end, so I would not be able to get up. But I’m too much of a pussy, and my head is too small.”

His mom saved him in more ways than one. When he was struggling with Crohn’s, she tried to find ways to motivate him. “Some days he was in so much pain, he couldn’t get out of bed,” Amy Davidson says in an email. “I used to bribe him and say, ‘If you get up and try to make the day you can go to the city later and do stand-up.’ We had a deal! That’s how he made it through high school. He is one of the strongest and bravest people I know.”

Peggy Sirota for Variety

On the streets of New York, a hyperventilating fan approaches Davidson, asking for a selfie.

“Are you Pete Davidson?” she gasps.

“Unfortunately, yes.”

“I liked you before the Ariana Grande thing,” she exhales, calling him one of her favorite celebrities.

“I’m not a celebrity,” he says. He poses for the picture. “Thank you.”

When we reach the apartment building, Davidson asks the doorman to let him up because he forgot his key. “Welcome to Ariana’s house,” he says, cracking open the door to their place. “I stock the fridge, clean the tables, do laundry occasionally.” The sprawling space is dimly lit and filled with unpacked boxes. Grande landed the 4,000-square-foot property in June for a reported $16 million. “I got the lawn chairs,” Davidson snickers as he sinks down into his bed. “I think I was a lawn chair in a past life.” The floor looks like a Foot Locker erupted, with at least two dozen pairs of sneakers. “I only wear two of them,” he says.

Falling in love with one of the most famous pop stars on Earth has brought a bigger magnifying glass on Davidson’s life. As a result, he quit social media and shut down his Instagram account. “The internet is evil, and I don’t like how it affects me,” he says. “I don’t like how the internet is a place where anybody can s— on you and make anything up. I’ve worked really hard to get my brain to this place. I can’t go online like everybody else because it’s just a f–k-fest. And now I get to enjoy my life.”

He offers a different analogy for the experience of Googling himself. “It’s like popping a pimple,” he says. “You’re like, ‘This is going to be sick.’ Then you do it, and you have to go to the dermatologist and get a cortisone shot, and there’s going to be a big hole in my face for a week.”

But there was one meme that didn’t bother him. The blogosphere championed the term “big-dick energy” for a man with abundant … swagger after seizing on a now deleted suggestive tweet between Grande and one of her fans. “I don’t hate it,” Davidson says. “I’m just really, really happy, and if that means I have big-dick energy, then sick.” He laughs. “My favorite thing was my mom was like, ‘Peter, they’re saying you had a big penis just like your father.’ What the f—!”

Davidson says that he didn’t plan to get married. “I never thought I’d meet anyone like her,” he says of Grande. “I can’t even put into words how great of a person she is. I could cry. She’s the f—ing coolest, hottest, nicest person I’ve ever met.” What would the 12-year-old Pete Davidson say about his life now? “I’m f—ing living the goddamn dream,” he says, standing up in his room. He grins. “I feel like I’m living in a fantasyland.”