By David Weigel, The Washington Post LOUISVILLE – Earlier this week, before heading downstairs to speak to nearly three thousand Kentuckians, Sen. Bernie Sanders, I-Vt., reminisced about his 2016 presidential campaign. After he had gained steam, and his rallies had become arena-size events, he was struck by the difference between his crowds and those at Democratic Party fundraisers. “We’d have a rally with five or ten thousand young people out, a great deal of energy,” Sanders said between bites of a steak sandwich.