PHILADELPHIA (AP) — Bernie Sanders tried to calm tensions among his delegates Monday at the Democratic National Convention but some weren’t in a listening mood, seething over a lengthy primary campaign and a damaging email disclosure.

Sanders’ delegates chanted the Vermont senator’s name during the start of the convention and booed lustily at any mention of rival Hillary Clinton. Behind the scenes, Sanders and his campaign tried to persuade his delegates not to disrupt the proceedings.

“Our credibility as a movement will be damaged by booing, turning of backs, walking out or other similar displays,” Sanders said in an email to the delegates, calling it a “personal courtesy” to him. He was speaking later Monday and as the evening dragged on, the signs of dissent were less visible.

Yet many die-hard backers of Sanders they weren’t ready to coalesce around Clinton’s presidential bid despite his pleas.

Their frustration was on display a day after Democratic party chair Debbie Wasserman Schultz announced she would step down at the end of the convention. Sanders’ loyalists heckled her at a Florida delegation breakfast and many expressed dismay that Clinton had given the Florida congresswoman the position of honorary chair of the campaign’s “50-state program.” She did not appear at the convention podium and later watched the proceedings from a private suite.

“I’m really annoyed,” said Michigan delegate Bruce Fealk. “I want to support Bernie, but I also want to voice my displeasure with the Democratic Party.”

Fealk said he viewed the emergence of hacked DNC emails, which suggested favoritism of Clinton, as a revelation and evidence of the party’s disrespect for progressives. Others said they simply couldn’t support Clinton.

“No, never, not in a million years, no. I wouldn’t vote for her for dog catcher,” said Melissa Arab, of Shelby Township, Michigan.

From the podium, however, some of Sanders’ allies noted their progress in influencing the party’s platform and moving to reduce the influence of superdelegates, party leaders and elected officials who help decide the nomination.

“I stand with my Democratic family in making sure we win this fall,” said Maine lawmaker Diane Russell, a Sanders supporter. “We are all in this together and we will all have a voice in the Clinton administration.”

Earlier, at a raucous meeting with his delegates, Sanders implored them to get behind Clinton and her running mate, Virginia Sen. Tim Kaine, and defeat Republican nominee Donald Trump.

“Make no mistake. We have made history,” Sanders told the crowd, stressing that their progress would be lost if Clinton doesn’t win. That appeal elicited boos and some cheers, as delegates shouted, “We want Bernie!”

Aides to Clinton and Sanders met before the start of the convention to find ways to prevent an open display of dissent, prompting the Vermont senator to send text and email messages requesting that they refrain from protests on the floor.

That was enough for Deborah Adams, of Cheraw, South Carolina, who served as a whip for the 14 Sanders delegates from her state’s delegation.

“I think every delegate should follow Senator Sanders’ request,” Adams said. “We’ve worked hard as a movement. It gives us a black eye if we don’t control our emotions.”