Nicole Gaudiano

USA TODAY

PHILADELPHIA – Bernie Sanders drew loud boos from his delegates Monday afternoon when he told the crowd of nearly 1,900, “We have got to elect Hillary Clinton.”

The eruption came during a speech in which the Vermont senator was cheered for nearly every point he made – including his call to defeat GOP nominee Donald Trump.

“This is the real world that we live in,” he said, following up his call to elect Clinton. "Trump is a bully and a demagogue. Trump has made bigotry and hatred the cornerstone of his campaign.”

Monday's meeting followed angry protests by Sanders supporters who already have hit Philadelphia's streets to oppose Clinton's nomination. Sanders has endorsed Clinton and has said he will do whatever is necessary to defeat Trump.

Michael Tafe of Hingham, Mass. said he and other Sanders delegates continue to believe the Vermont senator is the best candidate to defeat Trump and expressed unhappiness with Clinton's decision to choose Virginia Sen. Tim Kaine as her running mate..

“We feel alienated by the Clinton campaign,” he said. “They’ve made zero effort to reach out to us. Hillary’s VP choice is doubling down on her moderate platform and I think the people in this room are smart enough to realize once she gets into office, she’s just going to flip.”

Monday's convention events are taking place as delegates absorb Sunday's announcement by Rep. Debbie Wasserman Schultz of Florida that she will step down as chairwoman of the Democratic National Committee after the convention over leaked emails that reveal earlier DNC attempts to undermine Sanders' presidential campaign.

DNC Chair Debbie Wasserman Schulz to resign

Democrats had hoped to project an image of unity at the convention, but the emails make that more difficult. So does Clinton's appointment of Wasserman Schultz as honorary chairwoman of her campaign's 50-state program to elect Democrats.

"It kind of all reaffirms in the minds of Bernie delegates that we were given a raw deal, that we are dealing with a rigged system, that the primary was very much rigged from the very beginning in favor of Mrs. Clinton," said Karen Bernal, one of the leaders of the California Sanders delegation, during a morning news conference.

A majority of Sanders delegates surveyed in a straw poll said they want to protest the nominations of both Clinton and Kaine on the floor, said Norman Solomon, a Sanders delegate from California and national coordinator of the independent "Bernie Delegates Network."

"If Hillary Clinton wants to move today towards more party unity, she certainly has it within her power to say it’s a mistake to make an honorary chair out of Debbie Wasserman Schultz," Solomon said. "We shouldn’t be honoring someone who ran such a, we now know, disreputable shop at the DNC."

Sanders issued a statement Sunday saying Wasserman Schultz "has made the right decision for the future of the Democratic Party."

"While she deserves thanks for her years of service, the party now needs new leadership that will open the doors of the party and welcome in working people and young people," Sanders said. "The party leadership must also always remain impartial in the presidential nominating process, something which did not occur in the 2016 race."

In appearances on talk shows earlier Sunday, Sanders had again called for Wasserman Schultz’s resignation but said Democrats should focus on defeating Trump, whom he called “perhaps the worst Republican candidate that I’ve seen in my lifetime.”

“We have to elect Secretary Clinton, who on every single issue — fighting for the middle class, on health care, on climate change — is a far, far superior candidate to Trump,” Sanders said on Meet the Press. “That’s where I think the focus has got to be.”

Sanders’ will hammer that point home in his speech Monday and will "rip into Trump” for denying climate change is real, according to his campaign. He also will note the “most progressive platform in Democratic Party history” includes agreements he reached with Clinton to expand access to health care and make public college tuition-free for students from families with annual incomes up to $125,000 a year.

Bernie Sanders to address convention amid drama over leaked emails

Sanders also will tell the 13 million voters who supported him during the primary season that the political revolution they helped him launch continues, according to the campaign.

“Together, we continue the fight to create a government which represents all of us, and not just the 1 percent," he will say, according to the campaign. "A government based on the principles of economic, social, racial and environmental justice.”

Deborah Burger, a president of National Nurses United, said she assumes Sanders will call for unity in his speech. “But some of us have a different political agenda,” she said. “Some of our nurses aren’t ready yet (to endorse Clinton).”

Unlike Sen. Ted Cruz of Texas, who shocked the GOP's national convention in Cleveland last week by not endorsing Trump during his speech, Sanders endorsed Clinton at a New Hampshire rally on July 12 and said he will do everything he can to help her defeat Trump.

“Will I be very active in this campaign? The answer is, I will, and that will start after the convention,” he told USA TODAY on July 14.

Sanders will address the Democratic convention the same night that first lady Michelle Obama and immigration activist Astrid Silva will speak. Convention officials said the night's “United Together” theme will focus on building an economy that works for everyone, “not just those at the top” – one of the mantras of Sanders’ campaign.

Outside the convention, thousands of Sanders’ supporters are expected to protest party leadership and call for reforms.

Hundreds rally for Bernie Sanders in Philly heat

On Saturday, Sanders' campaign announced that the convention Rules Committee approved a “unity reform commission” charged with reducing the number of superdelegates, the party leaders and elected officials who may vote for the candidate of their choice at the convention. Sanders has called for abolishing superdelegates, who he believes gave Clinton an unfair advantage with early support.

The campaign said the commission will tackle caucus and primary reforms designed to make the nominating process fairer. The commission will recommend reforms to broaden the base of the Democratic Party, make it more responsive to the grassroots of the party and decrease the party's reliance on large donors, according to the campaign.

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