He won by playing it cool.

The successful candidate in the Democratic mayoral primary, Zohran Mamdani, experienced a surge in popularity among younger voters, as noted by Democratic observers. This increase in support came as comedians and influencers criticized the disconnected approach of former Governor Andrew Cuomo.

At 33 years old, Mamdani, a socialist, effectively utilized his online presence, which was enhanced by his expertly crafted social media content. This approach resonated with the humor prevalent among Millennials and Gen Z, in stark contrast to the outdated social media tactics employed by the 67-year-old Cuomo.

Comedian Nick Mullen, based in New York City, humorously emphasized the importance of younger voters in a video posted on Instagram, where he poked fun at Cuomo. Mullen’s video, shared alongside Mamdani the day before the primaries, highlighted the need for men in their 30s and 40s who engage with podcasts to participate in the electoral process.

“I cannot listen to Andrew Cuomo ever again,” added Mullen, who donated to Mamdani’s campaign, to his 213,000 followers in a video that scored more than 50,000 likes.

While Mamdani’s primary win last month seemed to come out of nowhere to some, it didn’t to 20- to 30-somethings across the five boroughs.

Nearly every major poll projected a fairly easy Cuomo victory — but they clearly neglected to capture to the scope of Mamdani’s digital grassroots mega-movement.

Mullen’s post was one of many reels and TikTok videos from Mamdani’s base that garnered hundreds of thousands of views, reaching young voters in a way Cuomo’s didn’t, a review by The Post found.

In exchange for $2,000 from the Mamdani campaign, comedian Jeffrey Seal wrote, directed and starred in a nearly 6-minute video that follows the “Journalist” around the Big Apple as he tried to find the elusive Cuomo.

The cheeky short — which racked up 1.2 million views — is chockful of hits to Cuomo’s record and features iconic New Yorkers including comedian Ilana Glaser of “Broad City” and musician Reggie Watts.

On the morning of the primaries, Mamdani also filmed another social video with supermodel Emily Ratajkowski.

The proof of Mamdani’s sleeper popularity was in the primary results — with him destroying Cuomo in a historic upset, taking home a 56% to 44% victory in the third round of the city’s ranked choice voting — and winning the popular vote in every round before that.

While complete voter age data won’t be released by election officials until July 15, polls by Emerson and Marist from May and June had shown Mamdani leading with voters under 45 by as much as a 2:1 ratio against the former governor.

Zohran spent more than $85,000 on video production, not including TV Ads, while Cuomo’s strategy hinged heavily on staid union endorsements along with name recognition and an older voter base.

Alyssa Cass, a partner at Sling Shot Strategies who ran Scott Stringer’s failed bid for mayor, gave props to Mamdani’s strategy.

“It really mattered, it made it part of the culture in a way that none of us were seeing,” she said of his online, take-it-to-the-streets tactics.

“Visibly matters a lot in mayoral races, and he became the only candidate that anyone talked about.

 “I even forgot Cuomo had a logo. He ran it like it was Bill Clinton, like it was 1992 race,” she said.

A Post review of the ex-governor’s social-media accounts found no instances of the legacy politician intentionally engaging with voters under 45. The former governor notoriously conducted most of his appearances in secure venues and used concert-style paper wrist bands to identify attendees of his events, which became a laughing matter among reporters and others attending them.

“This may come as a surprise to Cuomo and his irrelevant consultant friends, but only going to  protected event spaces filled with paid attendees is more outdated than a North Korean military parade,” a Dem strategist said.

Rich Azzopardi, a spokesman for the Cuomo campaign, told The Post, “There is no doubt we could have done more to reach out to younger voters, and that’s one of the issues currently under review as we consider next steps.”

One standout moment of Mamdani’s campaign came the Friday before the primary, when the Queens state assemblyman traversed the length of Manhattan — of course capturing the 13.4 mile journey on video to share with his 1.1 million followers on TikTok.

“On Friday night, we walked the length of Manhattan, from Inwood Hill to Battery Park. Because New Yorkers deserve a Mayor they can hear, see and even yell at if they need to. We out here,” Mamdani wrote in the caption.

Mamdani’s rep did not respond to Post requests for comment.