Despite our best hopes and struggle, Bernie Sanders’s presidential campaign once again ended in second place.But while we came up short, it’s more than clear now that 2016 wasn’t a fluke — we do indeed have a mass constituency. And those Bernie supporters deserve a vehicle to advance their political project in the years to come — that means a formal organization capable of representing and galvanizing a mass movement. What form that organization should take, however, is up for debate.