With Hillary Clinton now the presumptive Democratic nominee, Bernie Sanders, reeling from a decisive loss in California on Tuesday night, will lay off more than half his campaign staff, The New York Times reports, with the bulk of the cuts among advance staffers and field staffers. The grassroots fundraising machine that fueled his insurgent candidacy, sometimes bringing in more than $40 million a month, had collapsed in May after his losses in several states. And with only the Washington, D.C., primary left in the race, there’s no rational reason to keep his nationwide network of staffers together.

Sanders still refuses to concede, however, despite losing Tuesday night to Clinton in four out of six states—including the delegate jackpot of California. “Next Tuesday we continue the fight,” he told a roaring crowd of supporters at a Santa Monica rally. “We are going to fight hard to win the primary in Washington, D.C., and then we take our fight for social, economic, racial, and environmental justice to Philadelphia. . . . The struggle continues.” Judging by the crowd’s reaction, they did not want Sanders to concede, either; some supporters told CNN that they would refuse to vote for Clinton and would instead support a third-party candidacy or write in Sanders’s name for president.

What is driving Sanders to remain in the race is something of a mystery to political watchers. But according to sources close to the Vermont senator, it’s his own rage and resentment that has fueled his passion to keep fighting against the odds. Politico reports that Sanders, who oversees nearly every detail in the campaign “right down to the bills,” has shot down numerous attempts by others within his campaign to get him to dial back his anti-corporate messaging or soften his anti-D.N.C. tone, even when it has harmed his campaign. Last month, for example, after Sanders released a statement barely condemning his supporters’ violent behavior at the Nevada Democratic convention, rapid-response director Mike Casca asked in an e-mail why they were “actively destroying what Bernie worked so hard to build over the last year just to pick up two fucking delegates in a state he lost.”

With the Democratic primary virtually over, the Sanders campaign has two options: either engage in an incredibly long-shot campaign to win over the 500-plus super-delegates he would need to win the nomination, or leverage his pledged delegates to turn July’s convention into a referendum on the super-delegate system itself, returning his campaign to the protest movement that it began as. This time, however, Sanders’s microphone is much larger, and the stakes are higher. No one, after all, expected Donald Trump to be Clinton’s challenger, and with the Democrats facing a big, orange existential crisis, Sanders could still make trouble for the D.N.C. if he so chooses.