Because the members of the Democratic establishment have made it clear that they will deny him the nomination even if he has 49% of the vote? If you’re so concerned about party unity why aren’t you wagging your bony finger at Hillary Clinton for trashing the front runner publicly and declining to say she would endorse him until she was shamed into doing it? Why aren’t you pestering Tom Perez to ensure an impartial convention process? Why do you spend your days tsk tsk-ing someone with no power if you care so goddamn much?