Last June, while digging through 50 boxes of archival material about Bernie Sanders’s four terms as the mayor of Burlington, Vermont, a reporter for the British newspaper the Guardian found a poem by Allen Ginsberg. Written by hand on a 1986 visit to the city, “Burlington Snow” didn’t name Sanders, but he was clearly the populist muse that inspired it. Ginsberg wrote, “Socialist snow on the streets / Socialist talk in the Maverick Bookstore / So…