Joe Biden has accepted the Democratic presidential nomination with a vow to be a unifying "ally of the light" who would move an America in crisis past the chaos of President Donald Trump's tenure.

In his strongest remarks of the campaign, Mr Biden spoke on Thursday both of returning the United States to its traditional leadership role in the world and of the deeply personal challenges that shaped his life.

Virtually every sentence of his 22-minute speech was designed to present a sharp, yet hopeful, contrast to the Republican incumbent.

"Here and now I give you my word: If you entrust me with the presidency, I will draw on the best of us, not the worst. l'll be an ally of the light, not the darkness," Mr Biden said.

"Make no mistake, united we can and will overcome this season of darkness in America."

For Mr Biden, 77, the final night of the Democratic National Convention was bittersweet. He accepted a nomination that had eluded him for over three decades because of personal tragedy, political stumbles and rivals who proved more dynamic.

But coronavirus denied him the typical celebration, complete with the customary balloon drop that both parties often use to fete their new nominees. Instead, Mr Biden spoke to a largely empty arena near his Delaware home.

Afterwards, fireworks lit the sky outside the arena where supporters waited in a car park, honking horns and flashing headlights in a moment that finally lent a jovial feel to the event.

The keynote address was the speech of a lifetime for Biden, who would be the oldest president ever elected if he defeats Donald Trump in November.

Mr Trump, who is 74, publicly doubts Biden's mental capacity and calls him "Slow Joe", but with the nation watching, he was firm and clear.

Still, the convention leaned on a younger generation earlier in the night to help energise his sprawling coalition.

Tammy Duckworth, an Illinois senator who lost both legs in Iraq and is raising two young children, said Mr Biden has "common decency".

Cory Booker, only the ninth African American senator in US history, said Mr Biden believes in the dignity of all working Americans.

And Pete Buttigieg, a 38-year-old former mayor and a gay military veteran, noted that Mr Biden came out in favour of same-sex marriage as vice president even before former president Barack Obama.

"Joe Biden is right, this is a contest for the soul of the nation. And to me that contest is not between good Americans and evil Americans," Mr Buttigieg said.
"It's the struggle to call out what is good for every American."

Above all, Mr Biden focused on uniting the nation as Americans grapple with the long and fearful health crisis, the related economic devastation, a national awakening on racial justice - and Mr Trump, who stirs heated emotions from all sides.

Mr Biden's positive focus Thursday night marked a break from the dire warnings offered by Mr Obama and others the night before.

The 44th president of the United States warned that American democracy itself could falter if Mr Trump is re-elected, while Mr Biden's running mate, Kamala Harris, the 55-year-old California senator and daughter of Jamaican and Indian immigrants, warned that Americans' lives and livelihoods were at risk.

Mr Biden's Democratic Party has sought this week to put forward a cohesive vision of values and policy priorities, highlighting efforts to combat climate change, tighten gun laws and embrace a humane immigration policy.

They have drawn a sharp contrast with Mr Trump's policies and personality, portraying him as cruel, self-centred and woefully unprepared to manage virtually any of the nation's mounting crises and policy challenges.

Mr Biden's call for unity comes as some strategists worry that Democrats cannot retake the White House simply by tearing Mr Trump down, that Mr Biden needs to give his sprawling coalition something to vote for.

Though he has been in the public spotlight for decades as a Delaware senator, much of the electorate knows little about Mr Biden's background before he began serving as Mr Obama's vice president in 2008.

Thursday's convention served as a national reintroduction of sorts that drew on some of the most painful moments of his life.

"I know how mean and cruel and unfair life can be sometimes," Mr Biden said. He added: "I found the best way through pain and loss and grief is to find purpose."
As a schoolboy, he was mocked for a severe stutter. He became a widower at just 30 after losing his wife and infant daughter to a car accident. Five years ago, he buried his eldest son who had suffered from cancer.

Mr Biden has maintained a polling advantage over Mr Trump for much of the year, but it remains to be seen whether the Democratic nominee's approach to politics and policy will genuinely excite the coalition he is courting in an era of uncompromising partisanship.