Zohran Mamdani’s improbable ascent has been widely understood as a generational pivot, a resonant sign of the power of the youth vote when youth itself gets politically turned on. Even as so much about his claim to the Democratic nomination in New York City’s mayoral race has undergone intense scrutiny, one aspect remains underplayed — that the 33-year-old candidate may have won not because of the city’s demographics but rather despite them.

Mr. Mamdani clearly energized young voters. But in statistical terms, the young do not dominate. There are roughly a half-million more New Yorkers over 50 than those between the ages of 20 and 39. The city’s population, like its infrastructure, is simply getting older and older. During the past quarter-century the number of New Yorkers 65 and over increased by 53 percent, to 1.43 million. Since 2020 — and even with the devastations of a pandemic that left older people especially vulnerable — this age cohort has been the only one to grow.

But the lack of available exit polling makes it impossible to know what percent of older Democratic voters actually ranked Mr. Mamdani in first place (or at all). But polling data released the day before the primary showed Mr. Cuomo’s lead on him shrinking among voters over 60.

In the weeks both before the June 24 primary and since, I have talked to many people in middle age and well beyond it about the mayoral race, about the candidate (or candidates) they supported and, in instances in which they changed their minds, what prompted their shifts in allegiance or interest. The discussions inevitably came around to Mr. Mamdani, and boomer and Gen X parents routinely told me that even if they were not drawn to him initially — questioning his lack of experience and policies, some of which struck them as entirely unfeasible or even absurd — they had been moved by their children’s enthusiasm for him.

One friend, a longtime Andrew Cuomo supporter, was recently asked by her 17-year-old son whether she would vote for the former governor in the general election, and she said she would not. As much as she believed he would make a very good mayor, the “kids,” and her own in particular, had spoken. The future, she felt, belonged to them.

Others view the future in a more proprietary fashion. Earlier this week, someone writing under the handle Caitlin on X described an unpleasant encounter she had just had with a Mamdani antagonist. “A woman spent the entirety of my parents’ party last night insulting me to every guest because I support Zohran,” she offered. “Thanks to her, my parents, who had Cuomo prayer candles, just sent $1,000 to @ZohranKMamdani.”