Newly minted Democratic White House nominee Joe Biden said US President Donald Trump has “cloaked America in darkness for much too long”.
The former US vice-president said his rival has unleashed “too much anger, too much fear, too much division”.
His impassioned speech was the capstone of a political career spanning nearly half a century.
Mr Biden, 77, heads into the general election campaign with a clear lead in opinion polls over Mr Trump, 74.
But with 75 days to go until the election the Republican president has plenty of time to narrow the gap.
In his address from his hometown of Wilmington, Delaware, Mr Biden said: “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.
“I’ll be an ally of the light, not the darkness.
“It’s time for us, for we the people, to come together. And make no mistake, united we can and will overcome this season of darkness in America.
“We’ll choose hope over fear, facts over fiction, fairness over privilege.”
Mr Biden said “character is on the ballot” this November.