Sen. Bernie Sanders, I-Vt., was heckled while addressing a crowd of delegates Monday ahead of the Democratic National Convention in Philadelphia.
This meeting comes after angry protests by Sanders supporters who have hit the streets of Philadelphia to oppose Hillary Clinton's nomination.
"We have shown the entire world that our ideas are not some crazy, wild utopian fantasies. They are ideas supported by working people from one end of this country to the other," Sanders said, addressing his supporters.
"We showed that the American people want a bold progressive agenda that takes on the billionaire class, that fights for racial, social, economic and environmental justice and that will create a government that represents all Americans, and not just a handful of wealthy campaign contributors," Sanders added.
Sanders took the opportunity to call on his backers to help elect Clinton and to prevent a Trump presidency.
This comes just one day after outgoing party chief Debbie Wasserman Schultz resigned due to internal emails that supposedly showed the Democratic National Committee trying to push support for Clinton over Sanders.
Sanders' call to support Clinton and Kaine was met by a mix of cheers and boos for that reason.