The day after Assemblyman Zohran Mamdani rocked the nation’s largest city by becoming the presumptive Democratic mayoral nominee, New York’s political leaders declined to formally endorse him, and some donors to former Gov. Andrew M. Cuomo considered coalescing behind Mayor Eric Adams.

In an interview, Scott Rechler, one of the city’s biggest landlords, said that in a general election race between Mr. Mamdani, a 33-year-old democratic socialist, and Mr. Adams, he would put his support and potentially his financial resources behind the scandal-tarred incumbent.

Mr. Rechler, who donated $250,000 to a super PAC supporting Mr. Cuomo, expressed hope that the former governor and Mr. Adams, who is running in the general election as an independent, would not split the centrist vote.

“You want to have leadership that speaks to what New York is,” Mr. Rechler said. “It’s the capital of capitalism.”

Mr. Cuomo, who for months led in Democratic primary polls, continued on Wednesday to leave open the possibility that he would run in November on a third-party line. Polls and conventional political wisdom suggest that such a move would only enhance Mr. Mamdani’s chances, at the expense of Mr. Adams.

Bill Ackman, a hedge fund billionaire and supporter of President Trump who donated $500,000 to Mr. Cuomo’s super PAC, said on social media that he also “may ultimately support and endorse” Mr. Adams.