Bernie Sanders should stay in the race simply to show people they do not only have two choices to choose from as the two major political parties would want people to believe. There is a choice. He knows he has the momentum and popularity to possibly sway some people or give people the choice of actually having a democratic election.
Yes, Bernie Sanders should stay in the race. He vowed in the beginning to stay in the race until the end. That would be the party convention. It is very unlikely he will receive the nomination, but he should stay in to fulfill his promise as well as to influence the party platform. The convention is the time for candidates to drop out and show support for the nominee selected at the convention.
I do not support Bernie Sanders, so I would vouch for him to exit the race, as he does not interest me. If a candidate thinks about exiting the race, their decision should be based of their own thoughts, and their own only. Their decision should not be tainted by others.
Bernie Sanders should have called it quit like yesterday. All odds are against him and it is clear he is headed for a humiliating defeat. The best thing to do now is concede and support Hillary for the sake of the party. Who knows, may Hillary will appoint him as the secretary of state.