W hen I first met Rahm Emanuel, almost 25 years ago, he had a pretty solid reputation, in some quarters, as an arrogant prick. Rahm — even then, he needed only one name, like Cher or Snoop — was recognized by his fellow Democrats as a brilliant political tactician, which is how he had risen to become one of Bill Clinton’s chief enforcers in the White House. But he was also known to be self-certain, occasionally thuggish, and unusually crass. (For many years, there seemed to be a rule in journalism that one couldn’t write about Emanuel without prudishly noting...