An emotional Tim Walz issues a rallying cry for Democrats as he accepts the vice-presidential nomination - "We’ll sleep when we’re dead. And we’re gonna leave it all on the field," he told the party convention.
In a headline speech in Chicago, Kamala Harris's running mate touted his small-town upbringing and career as a teacher and coach.
It came after Oprah Winfrey made a surprise appearance on stage, telling the raucous crowd to back Harris in November.
Former US President Bill Clinton, in his 12th consecutive convention speech, hailed Harris as "extraordinary" and took aim at Donald Trump who he said "creates chaos".
Meanwhile, demonstrators are marching on the streets of Chicago for the fourth day running, protesting against US support for Israel's war in Gaza.
Earlier, Donald Trump appeared behind bullet-proof glass for his first outdoor rally since an assassination attempt in July.
The four-day convention formally anoints Harris as the Democratic presidential contender; Republicans celebrated Donald Trump at their party's convention last month.
