Former Jersey City, N.J., Mayor Steven Fulop had never lived in the five boroughs before he took the job of leading the Partnership for New York City. Since January he has launched a multifront assault against Mamdani’s proposed increases. As the business community’s primary mouthpiece, he has met with the mayor and state legislators and warned them that higher taxes could cause the city’s business elite to flee. He has written opinion columns and taken to television and social media, calling Mamdani’s plan a “political mistake.”