But it was his wife's support that painted the most hopeful and emotional picture of a Biden presidency. Jill Biden, speaking directly to wives, mothers and teachers just like her, described the devastation she felt watching the coronavirus pandemic ravage the nation. And she told the audience her husband could lead the nation through this hardship just as he has their family through many personal tragedies of their own.

"As a mother and a grandmother, as an American, I am heartbroken by the magnitude of this loss. By the failure to protect our communities. By every precious and irreplaceable life gone," she said. "Like so many of you, I'm left asking: How do I keep my family safe?"

Speaking from the Wilmington, Delaware, high school classroom where she taught English years ago, Mrs. Biden described "the anxiety that echoes down empty hallways" and the uncertainty that has come as schools grapple with whether to resume in-person teaching as the pandemic rages on.

"The burdens we carry are heavy, and we need someone with strong shoulders," Mrs. Biden said. "If we entrust this nation to Joe, he will do for your family what he did for ours: Bring us together and make us whole, carry us forward in our time of need, keep the promise of America for all of us."

And she pledged that if her husband is elected president, America's classrooms "will ring out with laughter and possibility once again."

During their decades in public life, Jill and Joe Biden have faced considerable personal loss. Shortly after getting elected as a senator, in 1972, Biden's first wife and young daughter were killed in a car crash, leaving him to raise his two sons alone. He married Jill about four years later, but the two faced tragedy together when Biden's son Beau died of brain cancer in 2015.

Both speak openly on the campaign trail about the challenges they've experienced, and on Tuesday night, Mrs. Biden recounted seeing her husband, just four days after Beau's funeral, "shave and put on his suit" and "walk out into a world empty of our son."

"He went back to work. That's just who he is," she said.

Mrs. Biden said that while at times she didn't understand how he did it, she understood why: "For you." She added that her husband's "strength of will is unstoppable" and "his faith is unshakable" because "his faith is in you — in us."