Pundits, pols, and Democratic voters have spent the past couple of months debating when Sen. Bernie Sanders should drop out, or arguing that he should have already. But Sanders didn’t just have a right to stay in the Democratic primary race until the end of the schedule. He had an obligation to. He owed it those millions of voters and the millions of donors who contributed more than $200 million to his bid to compete until he was mathematically eliminated.

Though the Associated Press’s tally showed Clinton hitting the overall number of delegates needed to clinch the nomination Monday night following a mini-burst of superdelegates, Sanders still had an argument for continuing, so long as she hadn’t reached a majority of pledged delegates. After Tuesday night’s primaries, however, that excuse will run out, and his arguments for holding out will be depleted.

He doesn’t have to drop out right away. He can wait until after Washington D.C. votes on June 14. He can rest for a couple of days back home in Vermont. But then it will be time to face the reality set Tuesday. At some point this evening, Sanders will be mathematically eliminated according to the metric that all small-d democrats believe should determine a nominee: among pledged delegates, of which Hillary Clinton will clinch a majority regardless of whether she narrowly wins or narrowly loses California and everywhere else (Montana, New Jersey, New Mexico, North Dakota, and South Dakota to be exact).

If the Sanders campaign—which is reportedly torn between camps—chooses to follow an aggressive path after he loses the pledged-delegate race and continues fighting into the convention to sway superdelegates to his side, he won’t just come off as a heel. He will fail, spectacularly, endangering both his legacy and Clinton’s chances in November.

The question over the past couple of months, and one that picked up in intensity after the Nevada state convention chaos in May, has been whether Sanders’ continued presence in the race well after it became exceedingly likely he would lose the nomination was seriously harming the party’s ability to win in November. The answer to this question was no, it was not. Sanders has made barbed comments about Clinton and some sharp critiques of the primary rules overall, even as his window closed. These things do not matter. The debate over whether Clinton was nastier when she was losing in 2008 than Sanders is in 2016 is a subjective one that can’t be neatly adjudicated, so we won’t bother to answer it. Let’s just say that the tenor at the end of neither campaign was or is especially uplifting. But none of that mattered in November of 2008, because once Clinton had conceded she did everything she could to rally her supporters to Barack Obama’s side. So if the late-stage nastiness of a primary fight doesn’t really matter in the end, it’s worth focusing on what good Sanders has done by staying in the race: bringing new, young voters into the process, accumulating more delegates to leave a forward-looking imprint in the party platform, and using the homing beam of presidential media attention to pressure DNC chair Debbie Wasserman Schultz into having fewer terrible political positions.

The lasting damage that so many have fretted about will only come if Sanders officially loses the pledged-delegate count and refuses to accept the results heading into the Philadelphia convention. If there were any way that withholding his concession could translate into his nomination, Sanders would owe it to his supporters to continue. But there is no way.

The Sanders campaign’s more aggressive faction, to which Sanders himself may be party, argues that the polls showing Sanders outperforms Clinton in a head-to-head matchup against Donald Trump make it a sort of fiduciary responsibility of superdelegates, as custodians of the Democratic Party, to give the nomination to Sanders. This won’t happen, and it shouldn’t. It won’t happen because (a) Sanders will have lost the pledged-delegate race, comfortably, and (b) the party officials who make up the superdelegation do not particularly care for Sanders. It’s the first part that matters more. Even if Sanders did have a warm, glowing relationship with Democratic Party bigwigs, it would destroy the party if they were to side with him over the pledged-delegate winner. The undemocratic nature of superdelegates is what led the Sanders campaign, correctly, to rail against their existence early in the process, before the campaign recognized that flipping superdelegates was its only remaining shot at the nomination. It’s not going to happen, it shouldn’t, and in the fantasy world where it did, Sanders would win the nomination by directly damaging the democratic ideals on which he campaigned.

But what about the specter of a Clinton indictment? Isn’t the possibility that the FBI throws the book at Hillary Clinton between now and the late-July convention a reason to keep his campaign alive? No. There are few federal crimes that I’m aware of, at least, that at the point of indictment penalize the perp by taking away some number of pledged delegates to a party’s convention. If Clinton is indicted and then superdelegates do show an interest in overturning the will of the voters—a doubly impossible scenario to imagine—then it will be a whole new game, and Sanders can unsuspend his campaign. That’s just the thing: In the scenario of a meteor hitting the Democratic Party, it won’t matter whether his campaign was active or idle at the moment of impact.

Just as the onus will be on Sanders to concede sooner rather than later, so too will it be Clinton’s duty to make concessions of her own. Though Clinton has argued that she conceded to Obama without conditions in 2008, that’s not entirely true: The Obama campaign and its allies worked to retire her campaign debt for years. The Clinton campaign has the opportunity and the responsibility to extend its own peace offering to Sanders. He has already earned slots for several of his top supporters on the platform drafting committee. Clinton’s team should go further and agree ahead of time to several of the planks about which he cares most deeply. If Sanders wants rule changes to future primary processes, Clinton should urge the Democratic National Committee to create a study commission on which his supporters will be represented. Let him speak whenever the hell he wants at the convention. Whatever.

However frisky things got in the last month, none of it will matter if Sanders concedes to the first female major-party presidential nominee once primary voters are finished voting. He owed it to his supporters in each state to keep fighting as long as he had an outside chance. After Tuesday’s primaries he will no longer have that outside chance. The only reasons he would have for not conceding are delusion or malice. Such a post-campaign campaign would alter his legacy in a way that he’d definitely come to regret.

Read more Slate coverage of the 2016 Democratic primary.