He's not really a Democrat at all ... never has been, never wanted to be; and that's what has some of the party leadership a bit ... ruffled. But those who work for the party and have been party supporters, will vote for him in November. If he doesn't win the nod, many of his supporters won't vote, because they won't support the party regardless and wouldn't have anyway. They couldn't possibly compromise their ideals any and find not voting more noble, which is their choice. But not voting, imo, is a vote for Rubio, Cruz or Trump, whoever wins the Rep nom. And Hillary can't attack Sanders and doesn't, not just because it's not good for the party, but she can't. I think Dave explained it best above.