You make the assumption that voting is done fairly and that every vote is counted. It is not. The DNC is known to divert votes from one to another. They can’t do it on a grand scale of course, which would make the scam too obvious. But where the race is close, votes will be moved to Hillary.
Already the DNC has removed or diverted millions of votes from both Bernie and Rocky De La Fuente, the third-placed candidate that few have even heard of. To win, Bernie has to get huge numbers against Clinton to overcome the system bias. However anything is possible I guess… As Trump said of his own primary campaign. It has to be a knockout punch, as we know the judges and system is biased against outsiders.