PHILADELPHIA (CBSNewYork/AP) — Sen. Bernie Sanders sought to unify the Democratic Party Monday night, calling on his supporters to back Hillary Clinton.

Coming out to chants of “Bernie, Bernie,” the senator said this election is about “the needs of the American people.”

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“Let me be as clear as I can be. This election is not about, and has never been about, Hillary Clinton, or Donald Trump, or Bernie Sanders or any of the other candidates who sought the presidency,” the Vermont senator said. “This election is not about political gossip. It’s not about polls. It’s not about campaign strategy. It’s not about fundraising. It’s not about all the things the media spends so much time discussing.”

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Sanders said Clinton must become president.

“By these measures, any objective observer will conclude that – based on her ideas and her leadership – Hillary Clinton must become the next president of the United States. The choice is not even close,” Sanders said, as the crowd was mixed with applause and boos.

Sanders touched on wages, Citizens United and the Supreme Court on why Americans need to back Clinton over the Republican presidential nominee.

“If you don’t believe this election is important, if you think you can sit it out, take a moment to think about the Supreme Court justices that Donald Trump would nominate and what that would mean to civil liberties, equal rights and the future of our country,” Sanders said.

Sanders said this election must bring the country together, not tear it apart.

“In these stressful times for our country, this election must be about bringing our people together, not dividing us up. While Donald Trump is busy insulting one group after another, Hillary Clinton understands that our diversity is one of our greatest strengths,” Sanders stated. “Yes, we become stronger when black and white, Latino, Asian-American, Native American – all of us – stand together. Yes, we become stronger when men and women, young and old, gay and straight, native born and immigrant fight to create the kind of country we all know we can become.”

Sanders told his supporters that he understands that they are disappointed, but that they have to take into account the movement they helped to create.

“I understand that many people here in this convention hall and around the country are disappointed about the final results of the nominating process. I think it’s fair to say that no one is more disappointed than I am. But to all of our supporters – here and around the country – I hope you take enormous pride in the historical accomplishments we have achieved,” he said.

Sanders continued, “Together, my friends, we have begun a political revolution to transform America and that revolution – our revolution – continues. Election days come and go. But the struggle of the people to create a government which represents all of us and not just the 1 percent – a government based on the principles of economic, social, racial and environmental justice – that struggle continues. And I look forward to being part of that struggle with you.”

However, he did tell his supporters, “I look forward to your votes during the roll call tomorrow night. “

Some Sanders supporters even broke down into tears during his speech.

Sanders talked about not seeing eye-to-eye with Clinton on certain issues, but that it’s time to unite behind her.

“It is no secret that Hillary Clinton and I disagree on a number of issues. That’s what this campaign has been about. That’s what democracy is about, but I am happy to tell you that at the Democratic Platform Committee there was a significant coming together between the two campaigns and we produced, by far, the most progressive platform in the history of the Democratic Party,” Sanders said. “Among many, many other strong provisions, the Democratic Party now calls for breaking up the major financial institutions on Wall Street and the passage of a 21st Century Glass-Steagall Act. It also calls for strong opposition to job-killing trade agreements like the Trans-Pacific Partnership.”

Clinton originally backed the Trans-Pacific Partnership, but has since changed her position.

Sanders said the job now is to vote in a Democratic Congress and to leave the White House in the party’s hands.

“Our job now is to see that a strong Democratic platform is implemented by a Democratic Senate, a Democratic House and a Hillary Clinton presidency – and I am going to do everything I can to make that happen,” Sanders said.

He finished his speech, “Hillary Clinton will make an outstanding president and I am proud to stand with her tonight.”

Before Sanders took the stage, first lady Michelle Obama and Sen. Elizabeth Warren also sought to unite Democrats behind Clinton.

“I want someone with the proven strength to persevere, someone who knows this job and takes it seriously, someone who understands the issues a president faces are not black and white,” Mrs. Obama said on the opening night of the Democratic convention. Referring to Trump’s penchant for tweeting, she said of the presidency: “It cannot be boiled down to 140 characters.”

Warren, a favorite of liberals, has emerged as one of the Democrats’ toughest critics of Trump, and she kept up her attacks on his character and business record as she delivered the night’s keynote address.

“Donald Trump has no real plans for jobs, for college kids, for seniors,” she said. “No plans to make anything great for anyone except rich guys like Donald Trump.”

The cheers from the audience masked real tensions that had spilled into the convention hall and onto the streets of sweltering Philadelphia earlier in the day.

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Sanders’ supporters arrived at the convention infuriated over leaked emails showing the Democratic National Committee had favored Clinton in the primaries, despite vows of neutrality.

They scored the resignation of party chair Debbie Wasserman Schultz, but still erupted in chants of “Bernie” and booed Clinton the first several times her name was mentioned during the convention program. Outside the convention hall, several hundred Sanders backers marched down Philadelphia’s sweltering streets with signs carrying messages such as “Never Hillary.”

Sanders and his team spent much of Monday trying to keep backers from protesting on the convention floor. He sent urgent emails and text messages urging them to avoid protests on the convention floor. The Clinton campaign opened up speaking spots for his supporters.

An array of office holders and celebrities hammered home the call for unity, with singer Paul Simon singing his “Bridge Over Troubled Water” as delegates linked arms and swayed to the music.

Former President Bill Clinton smiled and clapped from the audience.

Mrs. Obama was one of the night’s standouts. While she has often avoided overt politics during her nearly eight years in the White House, her frustration with Trump’s rise was evident. She warned that the White House couldn’t be in the hands of someone with “a thin skin or a tendency to lash out” or someone who tells voters the country can be great again.

“This right now, is the greatest country on earth,” she said.

Clinton’s campaign hoped the nighttime line-up would overshadow a tumultuous start to the four-day convention. The hacked DNC emails fed the suspicion of Sanders’ supporters and sapped Clinton’s campaign of some of its energy following a well-received rollout Sunday of her running mate, Virginia Sen. Tim Kaine.

Campaigning in North Carolina, Trump seemed to revel in the Democrats’ commotion, telling supporters that Clinton made a mistake by not choosing a more liberal running mate to appease Sanders’ base. “Crazy Bernie’s going crazy right now,” he said.

Trump tweeted during Sanders’ speech, “Sad to watch Bernie Sanders abandon his revolution. We welcome all voters who want to fix our rigged system and bring back our jobs.”

But in Philadelphia, delegates waved “Love Trumps Hate” signs and leapt to their feet as immigration supporters, gay rights advocates, and labor leaders took the stage.

Comedian-turned-Sen. Al Franken, a Clinton supporter, and actress Sarah Silverman, a Sanders supporter, made a joint appearance to promote party unity.

“I am proud to be part of Bernie’s movement,” Silverman said as the crowd roared. “And a vital part of that movement is making absolutely sure Hillary Clinton is our next president of the United States.”

Trump was a frequent target throughout the night, though the jabs were often more mocking than mean. The tone was a sharp contrast to the Republican convention, where the attacks against Clinton was bitingly personal, including chants of “Lock her up.”

Wasserman Schultz had planned to be among those taking the stage, despite the email hacking controversy. But she stepped aside, bowing to pressure from Democrats who feared the mere sight of her on stage would prompt strong opposition from Sanders’ backers.

The outgoing chairwoman did watch the gathering from a private suite at the arena.

Clinton’s team hoped Wasserman Schultz’s resignation — along with an apology from the DNC to Sanders and his supporters — would keep the convention floor calm.

Discussions between the two camps prompted Sanders to send emails and text messages to supporters asking them not to protest.

“Our credibility as a movement will be damaged by booing, turning of backs, walking out or other similar displays,” Sanders wrote.

Mayor Bill de Blasio told CBS2’s Marcia Kramer that Sanders’ delegates should realize they scored numerous victories.

“You’ve made the Democratic Party platform the most progressive that it’s been in decades and now let’s go do the work of electing Hillary Clinton and stopping Donald Trump,” de Blasio said.

The party infighting had echoes of last week’s Republican convention, where some major GOP leaders voiced their displeasure with Trump and others didn’t even show up. Clinton promised a stark contrast to the GOP gathering, saying she planned to highlight “success stories” and flesh out details of her proposed policies.

Sanders was a relatively unknown Vermont senator when he decided to challenge for the Democratic nomination. He stunned the Clinton campaign with his broad support among young people and liberals, as well as his online fundraising prowess. But he struggled to appeal to black voters and couldn’t match the former secretary of state’s ties to the Democratic establishment.

The controversy over some 19,000 leaked DNC emails, however, threatened to complicate those plans. The correspondence, posted by WikiLeaks over the weekend, showed top officials at the supposedly neutral DNC favoring Clinton over Sanders in the presidential primaries.

Clinton campaign officials blamed the hack, which is now being investigated by the FBI, on Russian military intelligence agencies. The campaign also accused Moscow of trying to meddle in the U.S. election and help Trump, who has said he might not necessarily defend NATO allies if they are attacked by Russia.

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