He would be perceived by many in the Democratic Party as a "Benedict Arnold."
how so? Hillary is the establishment. Bernie and Trump aren't.
But Trump is a Republican, so, Sanders would then be betraying the Democratic Party.
I would assume body snatching of some kind
it may take a combined effort from those two to defeat Hillary.
There you go, a fusion ticket: Trump/Sanders.
Laugh hysterically, because it would be the establishment types in both parties who would be hysterical if that came to pass.