Seen from above, the 2016 electoral map of New York City is blue with dots of red. Trump’s home district is blue, but across the water a red wedge slices into Brooklyn. Around that red wedge are districts where Hillary won 90 percent of the vote and Trump was lucky to get 5 percent. Inside it, he beat her in district after district. The voters who handed him that victory are the Chassidic Jews of Williamsburg who dress in fur hats and black caftans. Their districts, crammed in by hipsters and minorities, are a world away from the progressive activist...