Bernie Sanders is drowned with boos after telling his supporters they must elect Hillary Clinton

Bernie Sanders was met with jeers and boos in Philadelphia as he asked his supporters to elect Hillary Clinton and her running mate during a Monday event ahead of this week's Democratic National Convention.

"Secondly, immediately, right now, we have got to defeat Donald Trump," Sanders said. "And we have got to elect Hillary Clinton and Tim Kaine."

The imperative was met with a chorus of boos.

"Brothers and sisters," Sanders continued. "This is the real world that we live in."

"Trump is a bully and a demagogue," he continued. "Trump has made bigotry and hatred the cornerstone of his campaign. Throughout this campaign he has insulted Mexicans and Latinos. He has insulted Muslims. He has insulted women and African Americans."

The crowd chanted back, "We want Bernie!" 

"Thank you," said the Vermont senator, who recently endorsed Clinton after a spirited primary battle for the Democratic nomination.

Clinton is set to officially accept the Democratic nomination for president at the convention this week.

He added that Trump wouldn't follow the constitution.

Watch the moment below: