Sanders Vows to Fight Despite Clinton Becoming Presumptive Nominee

Clinton has obtained requisite number of delegates needed to get the nomination.

Sanders walked on stage to "Bernie!" chants from the crowd of several thousand and appeared with several members of his family.

At one point during the event, Sanders' fans chanted "no more fracking" too, highlighting a key difference in opinion between Sanders and Clinton.

Over the weekend, Sanders said that, in his view, the convention will be “contested" either way, since Clinton is relying on votes from those party officials to hit the necessary total.

Defending his decision to stay in the race, one of his most passionate surrogates, former Ohio Sen. Nina Turner, rallied the crowd with cheers to "fight on," and also promised to take his movement all the way to the convention. Speaking more broadly, musician Dave Matthews told the crowd that the senator and his campaign was just "the beginning."

Barring an overwhelming victory in California tomorrow that puts him in the lead in pledged delegates, it will be hard for Sanders to make a case to superdelegates, who so far have overwhelmingly shown no sign of switching allegiances. It would be unprecedented for them to overturn the popular vote, which Clinton still leads in as well.

"This campaign has been to me an extraordinary experience," Sanders continued during his evening rally. "As I look out as this country and see so many people who love this nation, but who know we can be so much more, it gives me enormous optimism about our future. When we began our campaign, our ideas were considered a fringe campaign and fringe ideas. That is not the case today."

Clinton said Monday that her campaign was focused on the six primaries that lay ahead Tuesday. She still has to be selected as the nominee at the upcoming convention.