In the summer of 2018, almost no one thought Alexandria Ocasio-Cortez could beat Joe Crowley. Crowley was a 10-term incumbent, the fourth-ranking Democrat in the House, a man some thought would one day be speaker. A 28-year-old former bartender and democratic socialist was the longest of long shots to succeed him. But ever since she did, the political establishment has been trying to decide whether to take her seriously.For a while it decided not to. The Missouri representative Emanuel Cleaver said the Democratic caucus did not need her “sniping”, while the then senator Claire McCaskill dismissed her as a “bright...