Lefties turned out in droves for Sunday’s “Tax the Rich” rally featuring Sen. Bernie Sanders in The Bronx — but Mayor Zohran Mamdani refused to show face as he walks a tightrope with Gov. Hochul over taxes. At least 1,000 people filled Lehman College’s sprawling performing arts center, where Sanders (I-Vt.) spent nearly an hour pushing his own proposal targeting the wealthy. “A few years ago, it was estimated that Elon Musk, the wealthiest man alive, paid an effective tax rate of less than 3.3%,