“This is a city that is at a tipping point, at a precipice unlike ever before,” Mr. Espaillat said as he stood next to Mr. Mamdani at the ornate United Palace theater in Upper Manhattan.

Mamdani calls himself a “democratic socialist” and, although he strenuously denies it, he’s arguably the closest thing this country has ever seen to a full-blown communist as a major-party nominee fo...

“Pot meets kettle,” one X user wrote under a clip of the senator’s chat with Fox.