Michelle Obama expresses empathy for White House staff ‘touched by this virus’ and urges Americans to vote.

The former first lady Michelle Obama, one of the Democratic Party’s most respected figures, delivered what the Biden campaign called her “closing argument” for Joseph R. Biden Jr.’s candidacy on Tuesday, speaking in deeply personal terms to Americans disillusioned by politics about the need to vote.

In a 24-minute video, Mrs. Obama appealed to parents and young people, white working-class Americans and people of color, lashing President Trump’s mismanagement of the coronavirus — “he continues to gaslight the American people by acting like this pandemic is not a real threat,” she said — and warning that Mr. Trump’s habit of stoking division could be an effective political tool. She urged voting as the best remedy.

“We can expect that this election will be won by the slimmest of margins, just like it was four years ago,” Mrs. Obama said. “A handful of votes per precinct in Pennsylvania, or Arizona, or Wisconsin, or Florida, or anywhere else will make all the difference.”

As she released the video on her own social media platforms, Mrs. Obama acknowledged Mr. Trump’s Covid-19 diagnosis. She alluded to his decision to return to the White House while still receiving treatment for the virus, and the choice to take a drive outside of the hospital on Sunday, a move that some medical experts saw as dangerous for the Secret Service agents around the president.

“My heart goes out to everyone touched by this virus, from those at the White House, especially the Secret Service and residence staff whose service ought never be taken for granted, to all those names and stories most of us will unfortunately never know,” she wrote on Twitter.

In the video, Mrs. Obama appeared to speak implicitly to white voters who are struggling economically and are put off by terms like white privilege.

“It is frustrating to hear some folks say that you’ve been the beneficiary of privilege, that the color of your skin gives you a head start,” she said. “But right now, the president and his allies are trying to tap into that frustration and distract from his breathtaking failures by giving folks someone to blame other than them. They’re stoking fears about Black and brown Americans.”

That approach, she said, is “morally wrong, and yes, it is racist. But that doesn’t mean it won’t work.”

“As a Black woman who has — like the overwhelming majority of people of color in this nation — done everything in my power to live a life of dignity, and service, and honesty, the knowledge that any of my fellow Americans is more afraid of me than the chaos we are living through right now, well, that hurts,” Mrs. Obama said.“Imagine how it feels to wake up every day and do your very best to uphold the values that this country claims to holds dear — truth, honor, decency — only to have those efforts met by scorn, not just by your fellow citizens, but by a sitting president.”

Mrs. Obama said on Twitter that she hesitated to release her message in the wake of Mr. Trump’s contracting the virus, but that “the drama of the past few days has only emphasized what’s at stake in this election — from the coronavirus to a constant drumbeat of fear, division, and chaos that’s threatening to spiral out of control.”