With his unexpected victory in Indiana and Donald Trump becoming the presumptive Republican nominee, Bernie Sanders faces a tough decision in the coming days. Should the Vermont senator drop out and help unite the Democrats to fight Trump? Or does the continued strength of Sanders’s movement mean that he should carry the fight to the convention, even if he is highly unlikely to win?

Despite winning the popular vote in Indiana, Sanders won’t see any substantive improvement in his delegate count because delegates are distributed proportionally. Moreover, given Clinton’s slim lead among pledged delegates and her overwhelming lead among the superdelegates, Sanders would need to win by much larger margins to close the gap, let alone defeat Clinton.

Sanders has been making a dubious argument for why he should stay in the race: that the Clinton-pledged superdelegates in states he’s won should flip to him, and because he’s supposedly a more viable general election candidate than Clinton. The former still wouldn’t give him the delegate lead, though, and current polling is hardly predictive of who is more electable in November.

In truth, Sanders has a better argument for the staying in the race, one that was made by Clinton and her followers in 2008: When you have a mass movement, you owe it to your supporters to fight as long as possible—to fight, in the words of Bill Clinton, “until the last dog dies.” As Howard Wolfson, Clinton’s onetime communications director, told Politico about the 2008 race, “Your head told you the math didn’t add up, but your heart said, we’re continuing to win states, we’re continuing to draw big crowds, and it’s very hard to walk away from a contest when you have millions of supporters who are clearly still determined to help you get elected.”

The fact that Sanders, this late in the race, can draw a majority of voters in Indiana means his revolution has yet to run its course. He owes it to his supporters in California and other late states to give them a chance to vote. Nor is a vote for Sanders meaningless, even if his loss is foreordained. The delegates he continues to rack up will give him a greater voice in the convention and allow his supporters to shape the party platform.