McArthur and other Sanders supporters are approaching the gathering with the enthusiasm that has powered the effort from the start — holding garage sales, delivering pizza and raising money online to pay for their travel to Philadelphia.

But their nerves are raw now over the Democratic Party’s perceived slights against the insurgent candidate and they are clinging to a bygone hope that Sanders can wrest the nomination from Hillary Clinton despite her overpowering lead in delegates.

As these super-fans chant “Bernie or bust,” Democratic officials are growing increasingly worried about dissent, especially after a recent state convention in Nevada turned raucous. Some of the Sanders backers who are going to the convention as delegates for him — and there are more than 1,400 — give party officials little reason for comfort.

“I don’t think we’re going to see a lot of violence, but we are going to see some screaming and shouting if the DNC doesn’t humanize itself,” McArthur, a 24-year-old administrative assistant in suburban Denver, said of the Democratic National Committee. “A little civil disobedience is OK. It’s part of being an American.”

Sanders delegates, in more than a half dozen interviews, say that while violence is not their goal for Philadelphia, party unity isn’t their priority, either. They don’t believe he has been treated fairly by the party establishment.

“Anything can happen,” said Jesica Marie Butler, 25, a Sanders delegate from Hawarden, Iowa, who volunteers for the campaign and is raising money on gofundme.com for her trip to Philadelphia. “This is a movement. This is a political revolution. It’s getting people involved in the process. We’re going to stick to it.”

Clinton only needs 90 more delegates to lock up the presidential nomination, a number she’s likely to reach June 7, the final major day of primary voting. She now leads Sanders by nearly 300 delegates won in primaries and caucuses, an advantage that grows when including superdelegates, or party officials who can back any candidate. Most of them, by far, say they will support Clinton.

Still, Sanders has shown no interest in letting up, despite concerns of many Clinton supporters that he is undermining her as Republicans coalesce around Donald Trump. Many Sanders delegates don’t want him to give up, either.

JoAnn Fujioka, a Sanders delegate from Denver, said she didn’t approve of the chaos in Nevada, where Sanders supporters shouted down speakers and, according to party officials, hurled chairs in protest. The state party chairwoman later received death threats and thousands of angry phone calls. Fujioka says Sanders supporters are determined, but idealistic and optimistic.

“We should do whatever we can to get him nominated,” she said. “We are in it to win it — as Bernie is.”

Without acknowledging the reality that the nomination is essentially out of reach, the Sanders campaign has signaled it will agitate for changes in the party’s platform and procedures, which could also disrupt the convention. Supporters want Sanders’ priorities, like a $15 minimum wage and stricter banking regulations, included in the platform, an agenda that is not binding on the nominee. They also want changes in how elections are run, criticizing superdelegates and restrictions on primary voting.

Ingrid Olson, 38, a Sanders delegate from Council Bluffs, Iowa, said: “I think open primaries should be available everywhere. I also believe in restorative rights for felons. I don’t agree with superdelegates unless superdelegates are going to follow the will of the people.”

The acrimony has reached such a pitch that several Sanders delegates say they don’t know if they can ever back Clinton.

“I don’t see any scenario where I would support her at the convention,” said David Johnson, 50, a delegate from West Branch, Iowa. But in the general election? “It’s a hard call for me. Nobody wants to see that insane Trump guy win.”

He said it’s a “ridiculous argument” to say Sanders delegates should stand down to avoid weakening Clinton in the fall.

“This is a competition,” he said. “Bernie Sanders isn’t running to prop up Hillary Clinton. He’s running to win.”

Some Sanders delegates don’t want to go too far. “No matter who the nominee is, we have to unite,” said Euell Santistevan Jr., 20, of suburban Denver.

But Cleo Dioletis, from Denver, said the Nevada blow-up showed how far the party establishment would go to silence Sanders’ supporters. “I am very concerned that credentials could be pulled for unjust causes,” he said.

Ashley Wolthuis, a realtor in Ogden, Utah, said worries have increased sharply among her fellow Sanders delegates after Nevada. And she said Sanders supporters feel shortchanged by the few slots the Democratic National Committee gave them on the standing committees that will govern how the convention operates.

Wolthuis said she was appalled at the chaos in Nevada. But, as a former Libertarian Party member who became a Democrat because of Sanders’ focus on overhauling money in politics, she’s not worried about a Sanders-led push causing Democrats heartburn.

“Hillary didn’t inspire me to join the Democratic Party, Bernie did, so it’s hard for me to not imagine following Bernie wherever he goes,” Wolthuis said.