Bernie Sanders Will Alone Decide What Happens Next. Here’s What He’s Thinking.

Bernie Sanders has run for president like a lone prophet, a solitary Jeremiah who scribbles sprawling end-of-days speeches on his yellow legal pad from his hotel room or his car. He has few advisers and even fewer confidantes. He delivers sermons to adoring crowds whom he usually later avoids. He often wishes he were back home in Vermont, tending to the wood stove.

Now, with the primary effectively over, Sanders will do one final thing by himself: decide how it ends.

On Wednesday morning, Sanders is flying from California to Vermont, where he will spend a day weighing his own future and his party’s. He will review plans drafted by his advisers and consider his next move. Will he fight to the convention, or concede to Hillary Clinton, who has clinched the delegates she needs to win? Will he seek to transform the party and risk bloodying his opponent, or step aside with a whisper?

No one, not even Sanders’ close aides, know exactly what he is thinking. At wild rally in Santa Monica on Tuesday night, Sanders gave a hint, but no clear answer.

“I am pretty good at arithmetic and I know that the fight in front of us is a very, very steep fight. But we will continue to fight for every vote and every delegate we can get!” Sanders said defiantly.

He promised to wage a fight in the final, dead-last, tiny Washington, D.C. primary. “We are going to fight hard to win the primary in Washington, DC and then we take our fight for social, economic, racial and environmental justice to Philadelphia, Pennsylvania!” Sanders said.

What exactly that means, and whether Sanders eventually will graciously step aside, will be up to him alone. It is a deeply emotional and personal decision, one Sanders will make with the bitter taste of a nasty primary lingering—and the sense that he was wronged by the Democratic Party and cheated.

“He now has to land the plane,” said former Vermont Gov. Howard Dean, who lost a bitter primary fight against John Kerry in 2004 and conceded the race. “The big question is, how does he use what he accomplished to move his cause forward?”

“Only he can decide that,” Dean added.

Sanders is far from any concrete decision. Campaigning in San Francisco on Tuesday, Sanders didn’t know what he would do next in the next twelve hours, much less the next twenty-four. By midday, he didn’t have a speech written for that evening. He had not yet decided whether his charter plane on Wednesday morning would go to Burlington or Washington, D.C. (He settled, finally, on Burlington.) And he didn’t know how hard he would fight against Hillary Clinton.

The Sanders who barnstormed in Santa Monica on Tuesday did not seem like a man ready to concede anything. He promised to try to win over superdelegates to his campaign, a near-impossible gamble that would overrule the popular vote, which has favored Clinton by a significant margin. If he contests the convention, he will do it knowing that he could permanently damage Hillary Clinton in the fight against Donald Trump.

On Thursday, Sanders will huddle at the White House with President Obama, who is likely to recommend that Sanders find a graceful exit. The president advised Sanders on a Sunday phone call that he is planning to endorse Clinton as early as this week.

There’s been little time to plan ahead. He has been thinking one day at a time, campaigning in California from San Diego to Sacramento and beyond, shuttling from one rally to the next and then to his hotel. He had staked everything on winning the biggest state in the Democratic primary, which he appeared to be losing by a large margin on Election Night.

“All of our thinking has been about winning California,” spokesman Michael Briggs, who is nearly always at Sanders’ side, said on Tuesday afternoon. “The last couple weeks have been nonstop.”

To make matters more complicated, Sanders’ mood has darkened since he began his campaign. During a lengthy interview with TIME for a cover story two weeks ago, he scowled in the San Diego sunlight, called the reporter a member of the “corporate media” and said that he didn’t want to waste his time. “They play very dirty,” he said about the Clintons. He snapped at another reporter in a televised news conference on Monday. “Is that a serious question?” he said. Sanders’ bitterness has made him a tougher negotiating partner, on issues ranging from settling the debates schedule with the Clinton campaign to heated and biting rhetoric against his opponents. It also may make it harder to concede.

Sanders has already said he wants to fight at the convention for a $15 minimum wage, a ban on fracking, Medicare-for-all, free college tuition and other progressive dream items on the Democratic Party platform. He’ll have complaints for the rules committee on how primaries are run, and he’ll have to decide what voice he wants on Clinton’s Cabinet. But until Sanders sits down and makes a concerted plan for the convention, his aides’ hands are tied. Clinton staffers have little idea what to expect.

The stakes are high. Pressure has been building on Sanders from Democrats who want to see him concede the nomination gracefully and bring his supporters to back Hillary Clinton. Democrats believe he risks dismantling the party and weakening Clinton against Donald Trump. Clinton insiders believe he has already hurt her, and they want him to make it better.

But trouble lies in both directions. If Sanders exits the race too early, he loses much of his influence. If he fights in what many, including his own allies, consider will be a futile battle at the convention, he will likewise waste his credibility, and his sway, Democrats say.

The Democratic convention’s drafting committee for the platform meets on Wednesday, and it will the opening salvo for both sides in hearing what comes next. His aides still think the Vermont senator can wait until after the Washington, D.C., primary on June 14 to make a final decision.

His allies believe that if he handles his exit gingerly, he will be able to gain concessions from the Clinton campaign, keep a semblance of his movement and return to the Senate more influential than ever before. That may be what he finally wins.

“Thank you all,” Sanders said on Tuesday, finishing his speech. “The struggle continues!”

The biggest struggle, however, will be Sanders’ own choice.