How — and where — Zohran Mamdani catapulted to the top of Democrats’ New York City mayoral primary

The numbers behind Zohran Mamdani’s upset performance over former Gov. Andrew Cuomo in New York City's Democratic mayoral primary.

Zohran Mamdani didn’t just score more first-place votes Tuesday night in New York City’s Democratic mayoral primary — he also prompted his closest rival, former Gov. Andrew Cuomo, to concede before the night was over, making the city’s ranked choice tabulation feel like a formality.

While Mamdani’s supporters claim the outcome was no surprise, Cuomo had widely been considered a probable first-round winner until the election, with Mamdani and allied candidates organizing to deny him a ranked-choice majority via cross-endorsements.

However, several key factors ultimately swung the race in Mamdani’s favor.

Two of the most recent pre-election, nonpartisan polls had Cuomo leading in the first round. Emerson College showed Cuomo ahead by 3 points in the first round, and before that Marist University showed Cuomo leading by 12 points in the first-choice tally. Mamdani finished the unofficial tally last night 7 points ahead.

But polls tend to be a lagging indicator based on time in the field and release dates, especially in primaries. You could see momentum for Mamdani between those two polls, and it’s possible his surge really did come with the broader electorate in the final days of the campaign. It’s also possible a municipal primary election is just a tough type of race to get accurate polling results.