PHILADELPHIA—Thursday night, Bernie Sanders’ most vocal delegates, the noisiest of whom can be found in the California section, will in some way seek to protest either the nomination of Hillary Clinton or some piece of party politics, such as the Trans-Pacific Partnership, with which they strenuously disagree. It is their last big moment to register complaints or promote their issues at a spectacle viewed by some 20 million people.

So what are they planning to do? They won’t say. It’s partially because they don’t want “Hillary’s people” getting word of it. Another reason? They may not be sure themselves of what they’re doing until the moment arrives.

“Hahahahaha,” laughed California Sanders delegate John Schnitzer as he walked out of a closed-door meeting for Sanders delegates in the downtown Marriott on Thursday afternoon. I had asked him for tonight’s plan. “I can’t say anything. I’ll just say: Of course we had discussions. We talked about it. I can’t say what we’re going to do. I just want to say that we’re doing everything we can to get a message out.”

“There’s a lot of talk about a lot of things,” said Jose Caballero, a Sanders California delegate from San Diego who serves as an ambassador between the state’s Clinton and Sanders delegates. “We all talk [at the closed-door meetings] about what actions we’re going to do—make sure we’re not being disrespectful … or not being seen as rabble-rousers,” he added, noting that the criticism of Sanders delegates from the convention’s first session had been received. “So we’ve been very disciplined about how we’ve been protesting the last couple of days—very visual, not as loud.”

So what’s going down tonight? Where’s the action gonna be? Caballero began to talk of certain strategies under discussion, but then cut himself off.

“Is this going to go to print right now?”

It’s not even that they have some exquisitely detailed plan ready to be executed with a series of nods between the principals, Return of the Jedi style. These are progressive activists. Vertical command structures aren’t how they roll. If anything is going to happen, it’s going to be organic.

“Let me put it this way,” said Norman Solomon, a California Sanders delegate and coordinator of the 1,250-member Bernie Delegates Network, when asked what was in store for tonight. “Last night, when I was with the California delegation, and the chants started ‘NO MORE WAR’ ”—this happened during former Defense Secretary Leon Panetta’s speech—“I was very surprised. I had no expectation of it.” That, he explained, was started by the Oregon delegation and picked up by the Californians and others.

The protests move horizontally. If there’s going to be a multistate walkout, it won’t be at the snap of the fingers. One delegation will start moving, and then the others will suddenly find their own feet moving underneath them toward the exits, swept up in the moment, much as Tuesday’s walkout unfolded, much as—in a way—the small-potatoes campaign of a rumpled socialist coalesced into a national movement.

“I’ll put it this way,” Solomon reiterated. “I would be astonished if everybody just sort of sat and clapped.”

Read more Slate coverage of the 2016 campaign.