PHILADELPHIA (KDKA/AP) – Seeking to bridge deep Democratic divides, Bernie Sanders robustly embraced his former rival Hillary Clinton Monday night as a champion for the same economic causes that enlivened his supporters, signaling it was time for them, too, to rally behind her in the campaign against Republican Donald Trump.

“Any objective observer will conclude that – based on her ideas and her leadership – Hillary Clinton must become the next president of the United States,” he declared in a headlining address on the opening night of the Democratic convention.

Sanders joined a high-wattage lineup of speakers, including first lady Michelle Obama who made a forceful, impassioned case for the Democratic nominee. Mrs. Obama’s address all but wiped away earlier tumult in the convention hall that had exposed lingering tensions between Clinton and Sanders supporters.

Mrs. Obama, who has spent nearly eight years in the White House avoiding political fights, took numerous swipes at Trump, all while avoiding mentioning him by name.

“This election and every election is about who will have the power to shape our children for the next four or eight years of their lives,” she said. “There is only one person I trust with that responsibility, only one person I believe is truly qualified to be president of the United States, and that is Hillary Clinton.”

(Photo Credit: Aaron P. Bernstein/Getty Images)

(Photo Credit: Aaron P. Bernstein/Getty Images)

While Sanders had endorsed Clinton previously, his remarks Monday marked his most vigorous and detailed praise of her qualifications for the presidency. It came at a crucial moment for Clinton’s campaign, on the heels of leaked emails suggesting the party had favored the former secretary of state through the primaries despite a vow of neutrality.

Sanders scored the resignation of party chair Debbie Wasserman Schultz, a nemesis in the primaries, but that wasn’t enough to quell the anger of supporters. As the convention opened, they still erupted in chants of “Bernie” and booed Clinton the first several times her name was mentioned. Outside the convention hall, several hundred marched down Philadelphia’s sweltering streets with signs carrying messages such as “Never Hillary.”

Behind the scenes, Sanders and Clinton aides joined forces to try to ease tensions. Clinton’s campaign quickly added more Sanders’ supporters to the speakers lineup. Sanders sent urgent messages to supporters asking them not to protest.

By the time Sanders took the stage for the night’s closing address, much of the anger had been overshadowed by speeches promoting party unity. Sanders did his part, imploring his supporters to consider a country under Trump’s leadership.

“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,” he said.

The one thing Clinton and Sanders delegates do seem united on is that Trump should not be president.

“When people think through Donald Trump, and realize this is a snake oil’s salesman who is saying all the right things, Western Pennsylvania people are a lot smarter than Donald Trump is giving them credit for,” U.S. Rep. Mike Doyle, of Pennsylvania, told KDKA-TV.

President Bill Clinton, watching from the audience, leapt to his feet and applauded, as did most of the delegates filling the convention arena.

Former President Clinton will address the convention Tuesday night.

“For her campaign, there’s no question, there’s no better campaigner than President Clinton, and I’m sure he’ll be in Western Pennsylvania many times,” said Nancy Patton Mills, the chair of the Allegheny County Democratic Party.

Sanders spoke just after Massachusetts. Sen. Elizabeth Warren, a favorite of liberals who has emerged as one of the Democrats’ toughest critics of Trump.

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

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 Saturday 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.

But in Philadelphia, Delegates waved “Love Trumps Hate” signs and cheered 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.

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

The Democratic National Committee released this statement earlier on Monday on the emails:

“On behalf of everyone at the DNC, we want to offer a deep and sincere apology to Senator Sanders, his supporters, and the entire Democratic Party for the inexcusable remarks made over email. These comments do not reflect the values of the DNC or our steadfast commitment to neutrality during the nominating process. The DNC does not — and will not — tolerate disrespectful language exhibited toward our candidates. Individual staffers have also rightfully apologized for their comments, and the DNC is taking appropriate action to ensure it never happens again.

“We are embarking on a convention today that — thanks to the great efforts of Secretary Clinton, her team, Senator Sanders, his team, and the entire Democratic Party — will show a forward-thinking and optimistic vision for America, as compared to the dark and pessimistic vision that the GOP presented last week in Cleveland. Our focus is on electing Hillary Clinton, Tim Kaine and Democrats across the country, thanks to Democratic Party that is strong, unified, and poised for victory in November.”

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(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)