If he were a politician, a role he's sometimes flirted with, Kelly would be the most popular one in the city. Earlier this year, he received a 70 percent approval rating, matching his highest ever (and nine points higher than Bloomberg's). Mitchell Moss, an NYU public-policy professor, has said the commissioner "radiates power." Thomas Reppetto, the author of NYPD: A City and Its Police, calls Kelly "the greatest police commissioner in the history of the city. He invented the playbook on terrorism from scratch."