Business leaders are threatening to leave New York City amid the unlikely ascension of Zohran Mamdani. This scenario has played out before—here’s what happened

• New York’s richest are balking at the mayoral frontrunner’s tax-the-rich proposal to make the city more affordable for working people. It’s a meltdown as old as time—but picking up and leaving isn’t as easy as it sounds.

With a leftist New York City politician appearing likely to be the Democratic mayoral candidate for the U.S.’ largest city, business interests are melting down over the prospects of his tax-the-rich platform aimed at improving basic services.

Zohran Mamdani...