As a woman running for president, Senator Elizabeth Warren of Massachusetts, a Democrat, was bound to encounter the likability bias: assert yourself as a man and you're seen as a boss, yet assert yourself as a woman, and you're seen as bossy. But a recent dig to Warren's likability came from a somewhat unexpected source, at a somewhat unexpected angle. In an interview with MSNBC, former Senator Claire McCaskill of Missouri, another Democrat, suggested that Warren was struggling with being "in command of the policy" and still being "relatable." Then McCaskill defined Warren's fundamental "challenge" like this: "[F]rankly, sometimes she comes very close to that professor I just wanted to be quiet." Beyond sounding like a professor, Warren is one -- the Leo Gottlieb Professor of Law, emerita, at Harvard University. But is sounding like a professor -- whatever that means -- a liability in politics? McCaskill has publicly support...