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 Biden, who served for eight years as her husband’s vice-president.

“A president’s words have the power to move markets, they can start wars or broker peace,” she said. “They can summon our better angels or awaken our worst instincts. You simply cannot fake your way through this job. As I’ve said before, being president doesn’t change who you are. It reveals who you are. Well, a presidential election can reveal who we are, too.”

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

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

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 pre-existing condition was trusting Donald Trump, and for that, he paid with his life.”

Most of the Republicans featured Monday have criticised Trump in the past.