Mrs. Clinton, alas, is more like a veteran coach — she's adept at telling others how to lie on her behalf. But she's not a natural liar herself, and it shows. At a time when the Democratic base craves authenticity (hence the mobs at Bernie Sanders rallies), Ms. Clinton seems utterly fabricated (hence her inability to get a capacity crowd at her announcement speech last month in New York City). Her best hope now would be to stop pandering to Mr. Sanders' fans and instead explain where she and Mr. Sanders differ on policy. But that would require a level of political authenticity she's forgotten how to fake convincingly.