Self-described democratic socialist Zohran Mamdani's unexpected upset in New York City's Democratic mayoral primary on Tuesday exhilarated progressive activists, who had banded together to prevent the more moderate former New York Governor Andrew Cuomo from triumphing.

New York City's high-profile mayoral primary this week shined a bright light on the nation’s ongoing experiment with ranked choice voting.

“New Yorkers didn’t know who Mamdani was just a few months ago.” We spoke with Eric Lach, who spent yesterday morning with the presumed winner of the mayoral primary, about the election results. Plus: