Left-Wing Supporters Boo as Bernie Sanders Says 'We Must Elect Hillary Clinton' His supporters chanted, "We want Bernie!"

 -- Supporters of Sen. Bernie Sanders booed and jeered when as the Vermont lawmaker and former presidential contender told them, "We must elect Hillary Clinton."

Appearing for the first time this week in Philadelphia, where the Democratic National Convention kicked off this afternoon, Sanders tried to control the room and his fans.

"Brothers and sisters, this is the real world that we live in," he said. “[Donald] Trump is a bully and a demagogue. Trump, Trump has made bigotry and hatred the cornerstone of his campaign.”

But the crowd, in the last sign of the party struggling for any sense of unity, chanted, “We want Bernie!”

Sanders focused most of his remarks on his accomplishments during the primary battle, including how well he performed with young voters and used the event as a call to action, urging his delegates to stay involved and work to elect progressive candidates moving forward.

The meeting was celeb-filled too and featured many of Sanders standard surrogates such as actress Rosario Dawson and rapper Killer Mike, who helped energize the room.

“The support we have received from every state in this country has been extraordinary, and the grass roots activism is unprecedented in modern American history,” he boomed. “Make no mistake about it, we have made history.”

After Sanders finished speaking, a whispered exchange between the Vermont senator and his wife was picked up by a hot microphone. According to ABC News producers at the venue, it sounded like Jane Sanders told her husband, "They don't know your name isn't being put in nomination." But there are some reports that she said "is" instead of "isn't."

Campaign spokesman Michael Briggs ABC News that Jane Sanders meant there will be a roll call vote tomorrow when Sanders’ delegates will be able to formally vote for him on the convention floor.

Emotions ran high throughout the event, and it was clear that the recent controversy regarding leaked emails from top staffers with the Democratic Party have only enflamed tensions. During the senator’s speech, some people cried, others pumped their fists in the air.

Within the Hawaii delegation, for example, one gentleman told ABC News he planned to vote for Clinton, but others emphatically said they would vote for third party candidates.

“I am hoping to feel better over the next few days to feel better about Hillary Clinton,” Dylan Hooser from Kaui, Hawaii said, but added that the last few days have only felt the group feel less unified with the larger party.

ABC News' MaryAlice Parks contributed to this report from Philadelphia.