Joe Biden has been handed a huge boost in the race to challenge President Donald Trump in November’s election.
Mr Biden, a former vice-president, won decisively in South Carolina’s primary, where voters chose which Democrat they want to be the party’s candidate.
Left-winger Bernie Sanders came second in South Carolina – the fourth state to vote in the months-long primary season – and remains in the lead overall.
Another 14 states vote on Super Tuesday this week.
By the end of Super Tuesday, it could become much clearer who the nominee will be.
This is Mr Biden’s first-ever victory in a primary in what is his third run for US president.
In a victory speech, the 77-year-old said: “Just days ago the press and the pundits had declared this candidacy dead. Now, thanks to all of you – the heart of the Democratic Party – we just won, and we’ve won big.”
What happened in South Carolina?
Mr Biden won 48.4% of the share, ahead of Mr Sanders on 19.9% and billionaire hedge-fund manager Tom Steyer on 11.3%. It is Mr Steyer’s best performance of the primaries, but he will now end his campaign, leaving seven candidates in the running.
Mr Biden had been pinning his hopes on a strong result in the southern state, after performing poorly in Iowa, New Hampshire and Nevada.
He regularly cited his strong support among African-Americans, and polls suggest an endorsement by influential black congressman James Clyburn significantly influenced voting patterns.