"Sanders supporters believe an arcane and biased nomination process will hand Clinton the nomination and leave the party with a candidate whose private email-server activities are still under FBI investigation and who was publicly rebuked by the State Department for breaking rules and putting her personal privacy above national security. They cite months of general election match-up polls showing Sanders as the stronger candidate against Trump, and worry that Clinton's unfavorables are the highest of any Democratic nominee in the last ten presidential cycles."
http://www.commondreams.org/views/2016/06/07/california-and-beyond-sanders-democrats-and-independents-needed-stop-trump