Not necessarily. Unless DemonRat party rules require it. More likely the DNC would pick a "more suitable" candidate, should The Messiah become untenable, or withdraw (like that going to happen..NOT). Remember this whole party and party candidate selection is aconstitutional, and in many respect alegal as well. The parties are free to nominate whomever they wish, at least up to the filing deadline in the individual states. Even after then, should the Anointed One be removed in disgrace, the electors pledged to him could just vote for the New Anointed One..say Hillary perhaps? Biden might find himself VP candidate with her Thighness, if he's lucky. If he's not he could be replaced as well, under some pretext or other, with one of Hillary's cronies.