CJ Gunther — Getty Images North America/Tribune Content Agency Former Democratic U.S. Senate candidate Graham Platner greets supporters following a speech last month in Blue Hill, Maine. Maine oysterman Graham Platner suspended his Senate campaign amid a hurricane of revelations, culminating in a sexual assault allegation credible enough that his own national political party abandoned him within hours. Before the scandals, his appeal, blue-collar affect, and progressive policy positions had catapulted him to stardom. Platner’s meteoric rise and fall is a lesson in the potential dangers of charismatic, unfiltered outsiders that’s just as relevant in business as in politics. Platner...