Hey - at least Bernie is honest - he's a freakin' socialist and proud of it. All the other liberals have to lie and call themselves 'progressives.'
The party with which Sanders is affiliated (the Socialists) is called the "Progressive Coalition" party. It solely exists in VT and has several legislators and the Mayorship of the largest city of Burlington. So even in this case, they don't have the cajones to officially call themselves the "Socialist" party.