AP Photo/Paul Sancya, File Senator Bernie Sanders speaks during the first day of the Democratic National Convention in Philadelphia. rules-logo-109.jpeg O n August 24, Senator Bernie Sanders stood before a crowd of supporters gathered in a community arts space in Burlington, Vermont, to unveil the next phase of his progressive movement. “Tonight I want to introduce you to a new, independent nonprofit organization that is called Our Revolution, which is inspired by the historic Bernie 2016 presidential campaign,” said Sanders at the event, which was livestreamed to some 300,000 supporters. The group, Sanders declared, “will be fighting at the grassroots level for changes in their local school boards, in their city councils, in their state legislatures and in their representation in Washington.” But the enthusiastic applause that greeted Sanders in Burlington contrasted sharply with the messy controversies and bad press dogging Our Revolution even before its official launch. On the same...