"Make no mistake about it—we have made history," a hoarse Bernie Sanders told a room full of adoring delegates on the first day of the Democratic National Convention (DNC) in Philadelphia on Monday.

"We have shown the entire world that our ideas are not some crazy, wild, utopian fantasies," he said, "they are ideas supported by working people from one end of this country to the other."

Sanders, who ticked off a list of primary season accomplishments—including winning 13 million votes and the support of 46 percent of pledged delegates—elicited cheers of "Bernie! Bernie!" when he said: "We're not fringe players anymore!"

His line marking the resignation of Democratic National Committee chair Debbie Wasserman Schultz also drew huge applause.

But when Sanders declared, "We have got to elect Hillary Clinton and Tim Kaine," he was met with boos.

"We want Bernie!" the crowd shouted, as he outlined the reasons why Donald Trump must be defeated.

National Nurses United co-president Deborah Burger, who was inside the room during Sanders' address, told Common Dreams that the senator from Vermont "gave the speech that he was supposed to give and I think he pretty much expected the response that he got."

"There are some people who have said, 'ok we're going to move on and work to elect Hillary Clinton because Donald Trump is obviously not good for the country,'" Burger said. "However, there was an equally large—or larger—group that has been frustrated by the entire process that the DNC has set up and aren't ready to either endorse Hillary Clinton, and/or work to get her elected."

While she remains frustrated at the party's stance on single-payer healthcare and the TransPacific Partnership (TPP), Burger, for her part, said she left Sanders' speech feeling hopeful. Noting that Sanders walked off stage to chants of "Thank you, Bernie," Burger said the message from the movement was: "You got us this far, we'll take it from here."

Watch the full speech below: