There is an electability question in Sanders, that mostly GOPers have been saying, that Clinton will win and Sanders wont. And GOP will do everything to defeat Clinton as well with emails.
Hillary Clinton is UNELECTABLE. Democrats can put anyone and still win except Hillary. Around 20% of Sanders supporters have said they would not vote if need be while only 4% of Clinton's supporters have. Sanders is getting a small cross-over vote from Republicans, he got a whopping 25% vote from Republicans from Vermont.
And he is sweeping the Independents. Like 60-70% & Hillary rest. The independents are the largest voting bloc, whoever gets it will LIKELY win.
Sanders is forming a Democrat-Independent-Young Voter coalition by expanding the pie & increasing turnout which could potentially sweep the elections like it has not been done in 30-40 years.
Hillary can't win - She can't even get 100% of the Progressive votes