Ahead of the start of the Democratic National Convention, Bernie Sanders held court in Philadelphia before a large group of supporters in an appearance that showed the party still has a steep hill to climb in uniting.

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During his speech, Sanders hailed the resignation of Debbie Wasserman Schultz, the convention chair who will step down following an email hack that provided proof for Sanders supporters who claimed the party was behind Hillary Clinton all along. Sanders fans loudly cheered the moment along with the Vermont senator.

Speaking in Philadelphia, @BernieSanders supporters give rousing cheer to Debbie Wasserman Schultz resignation pic.twitter.com/L6DaBHeDVs — Mashable News (@MashableNews) July 25, 2016

But later, when Sanders offered an explicit endorsement of Clinton, his supporters weren't happy with the call, loudly booing as he said, "We have got to elect Hillary Clinton and Tim Kaine." As the jeering lingered, Sanders waved a hand, calling the supporters, "brother and sisters," and continued to speak, underscoring his thoughts on Trump as a "bully and a demagogue."

Sanders supporters jeer and boo when he says that Hillary Clinton must be elected. #DemsInPhilly pic.twitter.com/EIl6LxKEin — Mashable News (@MashableNews) July 25, 2016

Just moments later, the crowd interrupted Sanders' speech with a loud chant of "We want Bernie." Sanders offered a "thank you" and continued speaking.

Sanders supporters break out in "We want Bernie" chants #DemsInPhilly pic.twitter.com/QnsYysepcr — Mashable News (@MashableNews) July 25, 2016

The crowd reaction was another bump in what's already started out as a rough first 24 hours in Philadelphia for the Democrats following extensive protests by Sanders supporters on Sunday.

Later Monday, Wasserman Schultz announced she would not bring the convention to order, a move likely aimed to help the party avoid an incident such as one last week's at the Republican convention in which Ted Cruz was loudly booed by Donald Trump delegates during his primetime speech.

Instead, Baltimore Mayor Stephanie Rawlings-Blake will have the honor.