Bernie Sanders was booed by supporters while speaking ahead of the Democratic National Convention in Philadelphia on Monday, July 25, after urging them to vote for Hillary Clinton.

The former Democratic presidential hopeful urged his hundreds of delegates at the Pennsylvania Convention Center to vote for Clinton while warning them that Republican presidential nominee, Donald Trump, is a threat to the Constitution.

“We have got to defeat Donald Trump and we have got to elect Hillary Clinton and Tim Kaine,” the Vermont senator told the crowd.

His supporters immediately started loudly booing and chanting, “No!” and “We want Bernie!”

“This is a real world we live in. Trump is a bully and a demagogue,” Sanders, 74, continued. “Trump has made bigotry and hatred the cornerstone of his campaign.”

Despite the uproar, 90 percent of Sanders supporters are expected to vote for Clinton in November, the Washington Post reports. As previously reported, New CNN/ORC polls released on Monday show that Trump has pulled slightly ahead of Democratic rival Clinton following the Republican National Convention last week.

Sanders is also expected to speak during the DNC and will address the scandal surrounding the thousands of leaked DNC emails, which allegedly reveal that the Democratic National Committee favored Clinton over Sanders.

The Democratic National Convention will run through Thursday, July 28, when Clinton is expected to become the official Democratic presidential candidate. The former Secretary of State is expected to formally accept her nomination during a speech on Thursday. 

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