PHILADELPHIA—The mood quickly turned from enthusiasm to anger when Bernie Sanders made a request of his delegates to the Democratic National Convention this afternoon. “We have got to elect Hillary Clinton and Tim Kaine,” Sanders told a gathering of delegates inside the Pennsylvania Convention Center, a message that was met with loud boos.

Attempting to forge ahead despite the obvious show of disapproval, Sanders warned against a Donald Trump presidency. “Trump has made bigotry and hatred the cornerstone of his campaign,” the senator said. But the crowd grew so agitated that he eventually had to stop speaking as cries of “We want Bernie!” rang out.

This display could signal chaos to come at the Democratic convention later on Monday night and as the week unfolds. Presidential nominating conventions are intended to be carefully stage-managed shows of party unity, but Democrats so far seem to be in turmoil.

On the eve of the convention, Debbie Wasserman Schultz announced she would resign as the chair of the Democratic National Committee in the wake of a leak of emails that seemed to indicate that Democratic officials wanted Hillary Clinton to win out over Sanders during the primary season.

Sanders cheered the resignation in his speech, saying it “opens up the possibility of new leadership at the top of the Democratic Party.” But the resignation won’t be enough to convince his supporters that everything has been set right.

Now, Bernie delegates are actively discussing the possibility of revolt. On Monday morning, Norman Solomon of the Bernie Delegates Network told reporters “the exact configurations of the protests are unclear, but it’s evident that a substantial majority of the polled survey delegates ... want to participate in protests on the floor.” His group is talking to Sanders delegates to see what they want to do at the convention.

Of course, protests may not come to pass. Insurrection could also be put down quickly. Whatever happens, it is unclear how much sway Bernie Sanders himself will have over the outcome. During his speech, the senator did not give explicit instructions to delegates as to how they should behave, beyond urging them to support Clinton as a way to defeat Trump.

The DNC email leak may have made the task of achieving party unity far more difficult.

“Bernie didn’t say no protest,” said Jose Caballero, identifying himself as a Sanders delegate from California. But even if Bernie did tell his supporters not to protest, that might not matter much. “If Bernie came out and said no protest, I don’t think it would make a difference. People are going to protest, regardless,” Caballero added. His justification: “A Bernie delegate is a person who was elected by the people that support Bernie’s values. We’re here representing them. … People that are at home, they’re booing, they’re angry, they’re upset. They don’t want us to stop.”

It was never going to be easy to convince the most ardent of Sanders supporters to support Clinton as the party’s presidential nominee. But the DNC email leak may have made the task of achieving party unity far more difficult.

“Now that all these emails have come out, confirming that the party was colluding with the Hillary Clinton campaign, it throws another wrench in it, and makes it  a little bit more sour,” said Amanda McIllmurray, who said she was with the Pennsylvania delegation. She added: “There’s been talk about protests both during Tim Kaine’s acceptance speech, and Hillary Clinton’s acceptance speech. I adamantly support people speaking out, using their First Amendment right, and expressing their discontent.”

Sanders may have already endorsed Clinton for the presidential nomination, but his followers haven't necessarily embraced his spirit of support for his opponent. “I didn’t think he was [going to],” Caballero said, reflecting on what Sanders had to say on Monday and his call to elect Clinton. “I don’t think a lot of people were [thinking] that he would say something like that.” Caballero added that he’s “heard about a possible sit-in” as one form of potential protest.

Some delegates felt crushed. “I’m so disappointed,” said Katharine Hadow, identifying herself as an Indiana delegate. “I don’t like being asked to support Hillary.” But, she added, what Bernie has to say certainly matters: “Of course it does, because I wouldn’t have worked so hard for him if I didn’t trust his judgement.”

Polls show that Sanders supporters have been coming around to support Clinton. But that doesn’t mean that everyone will. For now, at least some Bernie delegates seem determined not to go down without a fight. Sanders has suggested he can’t snap his fingers to make his supporters fall in line. The Democratic convention will be a test of how many of his followers are willing to give their vote to Clinton. It may also be a test of how much influence the senator ultimately has over his most ardent supporters.