General Discussion

Mr. Mamdani has privately tried to discourage his ideological ally from running. The mayor-elect and his team fear that another high-profile challenge from the left might compromise his own bid to push the Democratic establishment to support his affordability agenda.

Mr. Mamdani also may want to avoid the optics of having Mr. Ossé challenge the House Democratic leader, who endorsed Mr. Mamdani in October after months of negotiation.

The disagreement caused Mr. Ossé to be disinvited from Mr. Mamdani’s election night watch party, according to two people familiar with the matter, even though he has been a frequent presence at Mr. Mamdani’s campaign events. Instead, Mr. Ossé said he spent the night “with my constituents at D.S.A. events celebrating Zohran’s incredible win.”