DEMOCRATS unleashed sharp attacks on President Donald Trump as the party opened its virtual convention on Monday with a range of speakers including four moderate Republicans and Bernie Sanders, who urged voters to join them in supporting Joe Biden for president.

The most-anticipated moment of the convention’s first night was a video address from former first lady Michelle Obama that delivered a personal endorsement of Mr. Biden, who served for eight years as her husband’s vice-president.

“Donald Trump is the wrong president for our country,” she said. “He has had more than enough time to prove that he can do the job, but he is clearly in over his head. He cannot meet this moment. He simply cannot be who we need him to be for us.”

“It is what it is,” she added, a clear reference to Mr. Trump’s reaction when confronted in an interview with the country’s high death toll from the coronavirus.

Democrats attacked Mr. Trump on the pandemic, racial justice and the shattered economy. Mr. Sanders, the democratic socialist who was Mr. Biden’s closest challenger for the presidential nomination, said “at its most basic, this election is about preserving democracy.”

“In the midst of all of this, we have a president who is not only incapable of addressing these crises, but is leading us down the path of authoritarianism,” Mr. Sanders of Vermont said.

Mr. Biden, who will accept his party’s presidential nomination on Thursday, appeared in video snippets from earlier campaign appearances.

“I may be kidding myself, but I think people are ready,” Mr. Biden said of police reform in one such comment. “But we can’t let up.”

The Democrats abandoned plans for a live convention in Milwaukee due to the coronavirus, and the challenge of putting on an event solely through video and speeches without a live audience quickly became apparent, as the affair lacked the drama and emotion of a raucous arena.

But there were powerful moments — and sharp attacks on the Republican president. One speaker, Kristin Urquiza, spoke about her father, who died after contracting COVID-19.

“My father was a healthy 65-year-old,” she said. “His only preexisting condition was trusting Donald Trump, and for that, he paid with his life.”

Most of the Republicans featured Monday have criticized Mr. Trump in the past.

“We’re being taken down the wrong road by a president who has pitted one against the other,” former Ohio Governor John Kasich said. “I’m a lifelong Republican, but that attachment holds second place to my responsibility to my country. That’s why I’ve chosen to appear at this convention.”

Earlier on Monday, anticipating Mr. Kasich’s appearance, Mr. Trump criticized him. “He was a loser as a Republican and he’ll be a loser as a Democrat,” the President told reporters on Air Force One, mistakenly suggesting Mr. Kasich was changing parties.

The evening began with a montage of diverse voices singing “The National Anthem” and a video message from the family of George Floyd, whose death at the hands of Minneapolis police galvanized the “Black Lives Matter” movement.

Like other convention speakers, New York Governor Andrew Cuomo used the opportunity to tear into Mr. Trump’s handling of the coronavirus. Mr. Biden, who has called for masks to be required in public, has said Mr. Trump “waved the white flag and left the battlefield” in fighting the pandemic.

“Only a strong body can fight off the virus, and America’s divisions weakened it,” Mr. Cuomo said. “Donald Trump didn’t create the initial division. The division created Trump; he only made it worse.” — Bloomberg