PHILADELPHIA — Sen. Bernie Sanders, who rocked the Democratic establishment with his closer-than-expected fight for its presidential nomination, told his backers Monday to put aside personal feelings, help elect Hillary Clinton and defeat Donald Trump.

Sanders gave the final speech on the first night of the Democratic National Convention, on a day party leaders struggled to tamp down dissent from Sanders supporters and turn the focus to the November election.

His full-throated endorsement of Clinton stood in contrast to last week’s Republican convention, where the runner-up, Sen. Ted Cruz (R-Texas), didn’t say he would back the nominee, Trump.

First lady Michelle Obama played a key role in trying to heal the Democratic split, delivering a speech that sought to tout Clinton, gently bring Sanders supporters into the fold and smack Trump as thin-skinned and unqualified.

But most hinged on Sanders’ remarks. He was greeted first with uproarious cheers, sustained so long that he choked up before beginning.

After touting progressive causes, he came to his focus for the night: a forceful endorsement of Clinton.

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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,” Sanders said. He said the election was about the needs of the middle and working class, the influence of Wall Street and big campaign contributors on politics and the environment.

“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,” Sanders said, triggering a long applause. “The choice is not even close.”

Later, in closing out his speech, he said: “Hillary Clinton will make an outstanding president, and I am proud to stand with her.”

Sanders noted that his supporters forced Democrats to change several key platform planks, including a proposal to make college tuition free for students from families with annual incomes of $125,000 a year or less, oppose a trade agreement known as the Trans-Pacific Partnership and impose tougher bank regulations.

On the idea that his supporters might not vote in November, Sanders said: “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.”

But outside the sports arena, Sanders’ backers taunted party delegates walking through the gates, chanting: “Hell No, DNC. We won’t vote for Hillary.” Some carried signs saying not to blame them if Trump becomes the next president.

Meanwhile, Trump on Fox News attacked Sanders as making a move that was “very bad for his legacy.” He said Monday night that Sanders is now supporting Clinton rather than fight because he is exhausted from campaigning and “wants to go home and go to sleep.”

Former New York Mayor Rudy Giuliani, a Trump supporter, told Fox News that Sanders is speaking about the former secretary of state herself when he laments the “1 percent.”

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CNN commentator Van Jones, who formerly worked in the Obama administration, said the night’s speakers were less divisive than those of the Republican convention.

“Nobody here is hateful,” Jones said. Of the speakers, he said, “What they’re afraid of is, they’re afraid of being hated, and that’s what they’re standing up for.”

Politico’s Kyle Cheney wrote that “Democrats ended the night more optimistic than they began it.”

It was a tumultuous beginning for Democrats, who had hoped to showcase a united convention that would stand in contrast to a chaotic Republican counterpart last week in Cleveland.

Democrats instead began with a rift over the role of the DNC — a rift that broke open after the publication of emails that showed chairwoman Debbie Wasserman Schultz tilting the scales in favor of Clinton. Wasserman Schultz was forced to resign as the party tried to put the controversy to bed.

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Keeping the focus on Trump, Sen. Elizabeth Warren (D-Mass.), a favorite of the Sanders wing, bashed Trump for frequently filing bankruptcy, “ripping off” customers, rooting for an economic downturn so he could profit and “turning neighbor against neighbor.”

Warren called Trump “a man who should never be president.”

Earlier, Sanders told backers it’s time to focus on an immediate goal: stopping Trump, the billionaire real estate developer from Manhattan, from taking the White House. Sanders got cheers when he told them to defeat Trump, whom he called a demagogue who threatened the U.S. Constitution. Electing Trump was unthinkable, Sanders told them.

But there were even longer and more sustained boos when he told them to back Hillary.

“Immediately, right now, we’ve got to defeat Donald Trump and elect Hillary Clinton,” Sanders said, triggering howls that, for a moment, even shouted him down.

Trying to quiet them, Sanders said: “Brothers and sisters, brothers and sisters — this is the real world we live in,” signaling it was time to switch from the primary fight to the November election.

The crowd responded chanting: “We want Bernie!” for several minutes, causing him to pause.

Dan Cantor, a New Yorker and national director of the labor-backed Working Families Party, said, “It’s only a slim minority who are going to say ‘No way’ to Hillary. Donald Trump has raised the stakes.”

Cantor said Sanders backers should be “proud” the Democratic platform supports a $15-per-hour minimum wage, a call to break up big banks and changes to the primary election system.

“Now we need to move on to the next fight,” against Trump, Cantor said.

Others weren’t convinced.

“Bernie started this. But he’s not in control of it anymore,” said Jay Ballanca, a Sanders supporter from Salem, N.Y., northeast of Albany.

On the main stage as the program got under way, other speakers touted Clinton’s long record on many issues, such as children and the disabled, tax policy and immigration. Others sought to bash or mock Trump.

Sen. Bob Casey (D-Pa.) said for all of Trump’s promises to bring jobs back to America, many of the developer’s products are made overseas.

“Dress shirts: Bangladesh. Furniture: Turkey. Picture frames: India. Wineglasses: Slovenia. Neck ties: China,” Casey said.

Sen. Al Franken (D-Minn.) used his comedic skills to skewer Trump University as a scam. The former “Saturday Night Live” cast member called the Republican nominee a “megalomaniac” who only helped himself.

“I got my doctorate in megalomaniac studies from Trump University,” Franken said. He told delegates that “Trump University’s School of Ripping People Off is ranked second in the nation, right behind Bernie Madoff University,” a reference to the Wall Street broker convicted of scamming customers.

Trump faces lawsuits from students who say “Trump U” defrauded them.

With Laura Figueroa and Emily Ngo