Publicly, Mr. Sanders’s position is that he can still win the nomination if he persuades unpledged superdelegates — elected officials, party habitués and various others granted delegate status by virtue of their office or connections — to support him by the time they have to cast their vote at the convention in late July. So far, almost all the hundreds of superdelegates have said they will vote for Mrs. Clinton. None have publicly defected. Few seem likely to do so. But the possibility that they will gives Mr. Sanders a reason to keep campaigning, keep raising money and keep criticizing Mrs. Clinton and the party establishment. That gives him leverage.
What does he want?
In a word, influence. Mr. Sanders sees himself as not only a candidate but the leader of a political movement. To advance that movement, he wants to see his views reflected in the party’s official platform and at the convention. That could mean stronger platform language on the regulation of big banks, or a plank demanding free public college. Mr. Sanders is also seeking changes to the Democratic primary rules, including the abolition of superdelegates — though in the short term he wants their support — and the expansion of “open” primaries in which non-Democrats can vote for Democratic candidates.
The bottom line is that Sanders has the chance to continue to shape the narrative of the Democratic Party by staying in. He has forced Hillary to be far more progressive than she normally is, and by staying in, he can continue to influence her, which is probably a good thing for Democratic Party as a whole.