First lady Michelle Obama stepped into the presidential election Monday with a forceful, impassioned defense of Hillary Clinton, casting her as the only candidate who can be trusted as a role model for the nation’s children. She took numerous swipes at Republican Donald Trump, all without mentioning his 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,” Ms. Obama said on the opening night of the Democratic convention. “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.”

The first lady was among a high-wattage line-up of speakers taking the stage, all but wiping away earlier tumult that had exposed deep tensions between Ms. Clinton supporters and those loyal to her primary opponent Bernie Sanders.While Ms. Obama 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.

Mr. Sanders was taking the stage later in the night. He and his team spent much of Monday trying to keep backers from protesting on the convention floor. He sent urgent messages to his backers 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.

Massachusetts Sen. Elizabeth Warren, a favourite of liberals and one of the party’s toughest critics of Trump, took the stage and, in tune with the proceedings, exclaimed, “Thank you, Bernie.”“Trump thinks he can win votes by fanning the flames of fear and hatred. By turning neighbor against neighbor. By persuading you that the real problem in America is your fellow Americans people who don’t look like you, or don’t talk like you, or don’t worship like you.”

Ms. Clinton’s campaign hoped the night time line-up would overshadow a tumultuous start to the four-day convention. The release of hacked party emails revealed the Democratic National Committee had favoured Ms. Clinton over Mr. Sanders in the primary, despite vows of neutrality. The uproar led to the forced resignation of party chair Debbie Wasserman Schultz.

While her ouster was a major victory for Mr. Sanders, it wasn’t enough to ease the frustration of his supporters. Inside the arena, chants of “Bernie” echoed through the arena as the convention opened, and boos could be heard at times when Ms. Clinton’s name was raised. Outside the convention hall, several hundred backers of Mr. Sanders marched down Philadelphia’s sweltering streets with signs carrying messages such as “Never Hillary.”

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

Ms. Clinton’s team hoped Wasserman Schultz’s resignation along with an apology from the DNC to Mr. Sanders and his supporters would keep the convention floor calm.Discussions between the two camps prompted Mr. 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,” Mr. Sanders wrote.

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

Mr. 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 favouring Ms. Clinton over Mr. Sanders in the presidential primaries.

Ms. Clinton’s 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 Mr. Trump, who has said he might not necessarily defend NATO allies if they are attacked by Russia