Dark-horse socialist candidate Zohran Mamdani staged a stunning upset Tuesday night by knocking off former Gov. Andrew Cuomo in the Democratic mayoral primary. “Tonight we made history,” Mamdani told supporters at his victory party after midnight. “In the words of Nelson Mandela, ‘It always seems impossible until it is done.’ My friends, we have done it. I will be your Democratic nominee for the mayor of New York City.” The 33-year-old Queens assemblyman defied polls and expectations as...