For Andrew M. Cuomo, the rally rolling out a $20-an-hour minimum wage proposal was supposed to be a high point of his comeback campaign for mayor of New York City.

It did not go particularly well. On the stage of a claustrophobic conference room in Midtown, the former governor flubbed two key lines, at one point promising to “combat affordability.” Many of the laborers paid by their unions to attend appeared uninterested, chatting in the back throughout the speech.

And when it was over, Mr. Cuomo bee-lined to his waiting Dodge Charger, punched the gas past waiting reporters and made an illegal right-on-red turn.

He made no further public appearances that day last month, even with Primary Day weeks away.

Mr. Cuomo, who dominated New York for a decade as governor, entered the crowded field of Democrats back in March with the force of a steamroller and a dominant lead in the polls. He wore down the Democratic establishment until it lined up behind him, strong-armed unions and seeded a record-shattering super PAC that would eventually spend $25 million.

But even some of his allies said that up close, the campaign sometimes looked more like an listing ship, steered by an aging candidate who never really seemed to want to be there and showed little interest in reacquainting himself with the city he hoped to lead.

New Yorkers took note. And on Tuesday, a campaign that Mr. Cuomo, 67, had hoped would deliver retribution four years after his humiliating resignation as governor ended in another thumping rebuke instead. Voters preferred Zohran Mamdani, a 33-year-old state lawmaker whom Mr. Cuomo dismissed a woefully unqualified, by a comfortable margin.