The most populated city in the United States might also have the most polarizing mayoral race of any other. The New York City mayoral race features a disgraced former governor, a surging socialist, an incumbent with his own legal troubles, and other heavy hitters.

The decision by Ms. Ramos, a state senator from Queens, is at odds with her frequent criticism of Andrew M. Cuomo, including comments questioning his “mental acuity.”

Andrew Cuomo faced a two-hour pile-on Wednesday as eight other Democrats vying for the party’s nomination for New York City mayor spent their first debate attempting to knock the former governor off his perch.