Bernie Sanders made it clear that he represents a fake opposition to Hillary's coronation when he said that "Americans are sick of hearing about the damn emails." If he were sincerely challenging her candidacy, he wouldn't have so abjectly and obsequiously run to her defense. He's just in there to make it look like an election rather than a coronation.
In contrast, the GOP field isn't nearly as willing to stand behind the RNC's plans for handing the crown and scepter over to Bush the anointed.
Rather, the Donald has the GOP nomination in his pocket.