Most of the poll-leading Democrats running for president have said they support nationwide legalization of marijuana for recreational use.The exception atop the polls: former Vice President Joe Biden.He has proposed decriminalizing marijuana use and automatically expunging previous convictions. He also supports the use of cannabis for medical purposes and reclassifying it so the federal government can study its impact.“Biden believes no one should be in jail because of cannabis use,” his campaign’s criminal justice policy says.But Biden falls short of calling for the nationwide legalization of recreational marijuana.