Former first lady Michelle Obama speaks during the first night of the Democratic National Convention on Monday.

NEW YORK — Joe Biden introduced the breadth of his political coalition to a nation in crisis Monday night at the Democratic National Convention, giving voice to victims of the coronavirus pandemic, the related economic downturn and police violence and featuring both progressive Democrats and conservative Republicans united against President Donald Trump's reelection.

In taped excerpts released before the convention opening, former first lady Michelle Obama, wife of the nation's first Black president, vouched for Biden's empathy and experience. And the extraordinary ideological range of Biden's many messengers opening night was demonstrated by former presidential contenders from opposing parties: Vermont Sen. Bernie Sanders, a self-described democratic socialist who championed a multi-trillion-dollar universal health care plan, and Ohio's former Republican Gov. John Kasich, an anti-abortion conservative who spent decades fighting to cut government spending.

In her taped remarks, Obama called Biden a “profoundly decent man” who will “tell the truth and trust science,” drawing a sharp contrast between President Donald Trump and her husband's two-term vice president.

“He knows what it takes to rescue an economy, beat back a pandemic and lead our country,” she said. “He will make smart plans and manage a good team, and he will govern as someone who's lived a life that the rest of us can recognize.”

The former vice president won't deliver his formal remarks until Thursday night, but he made his first appearance just half an hour into Monday's event as he moderated a panel on racial justice.

Sanders declared: “My friends, I say to you, and to everyone who supported other candidates in this primary and to those who may have voted for Donald Trump in the last election: The future of our democracy is at stake. The future of our economy is at stake. The future of our planet is at stake.”

Kasich said his status as a lifelong Republican “holds second place to my responsibility to my country.”

“In normal times, something like this would probably never happen, but these are not normal times,” he said of his participation at the Democrats' convention. He added: “We can do better than what we've been seeing today, for sure.”

The unified message, outlined in excerpts of prerecorded speeches, came as Democrats launched the first presidential nominating convention of the coronavirus era. The all-virtual affair was the first without a central meeting place or cheering throngs. And there were real questions about whether the prime-time event would adequately energize the disparate factions Biden hopes to capture.

Republicans face a similar challenge next week.

Trump sought to undermine the Democrats' big night by hosting a political rally in Wisconsin, where Biden's party had originally planned this week's convention. He called the Democrats' event “a snooze” before it even began.

“You know when you hear a speech is taped, it's like there is nothing very exciting about it, right?” the Republican president said.

Monday's speeches were framed by emotional appearances.

Philonise and Rodney Floyd led a moment of silence in honor of their brother, George Floyd, the Minnesota man whose death while in police custody sparked a national moment of awakening on racial injustice.

“George should be alive today,” Philonise Floyd said matter-of-factly.

Kristin Urquiza, an Arizona woman who lost her father to COVID-19, which has killed more than 170,000 Americans as of Monday evening, said, “My dad was a healthy 65-year-old. His only preexisting condition was trusting Donald Trump, and for that, he paid with his life.”

And Rick Telecz, a Pennsylvania farmer, warned that Trump's trade war has had a “truly a devastating effect” on his farm before the coronavirus brought another blow with what he called “misinformation.”

“My biggest concern is that if these trends with this type of leadership, I will be the last generation farming this farm,” he said.

Democrats abandoned their plans for an in-person gathering in Milwaukee because of the pandemic. The gathering is not only testing the bonds of the diverse Biden-Kamala Harris coalition but the practical challenges of running a presidential campaign in the midst of a pandemic.