As the black SUV came to a stop on 33rd Street in Manhattan, its lights flashing, a pale hand stretched through the open window of the passenger door and gave a little wave. It was attached to Rudy Giuliani, who smiled from behind his tortoiseshell sunglasses. He apologized for being late. “Couldn’t go on sidewalks like I used to,” he said, mourning a perk of his past life as mayor.