In the final hours before Primary Day, the Democratic race for mayor of New York City appeared to be razor-tight, leaving the two leading candidates — Andrew Cuomo and Zohran Mamdani — in scramble mode to boost turnout on Tuesday.

A new poll released on Monday by Emerson College suggested the race was too close to call, with Mr. Cuomo drawing the most first-place votes but falling short of the 50 percent threshold required to be declared the winner under the city’s relatively new ranked-choice voting system.

The poll shows Mr. Mamdani pulling ahead in the eighth round, topping Mr. Cuomo by 3.6 percentage points — matching the poll’s margin of error. It is the first major survey that shows Mr. Mamdani winning, seemingly reflecting his momentum, especially among younger voters.

“It is essential that we turn out in record numbers in order to turn the page on Andrew Cuomo, his billionaire donors, and the politics of big money and small ideas,” Mr. Mamdani, a state assemblyman and democratic socialist, said on Monday.

Mr. Cuomo, the former governor who resigned in 2021 following a series of sexual harassment allegations that he denies, has led in polls for months, including one also released on Monday by Fix the City, a super PAC tied to Mr. Cuomo’s interests. His campaign called the Emerson poll an “outlier.”

“We will continue to fight for every vote like he will fight for every New Yorker as mayor,” Rich Azzopardi, a spokesman for Mr. Cuomo, said.