So it's still early, but momentum matters - especially in a race with so many candidates and so many undecided voters. On Wednesday NZT, as Biden will still be riding high on his win, voters in 14 states will cast ballots. Do Democratic voters who are worried about a Sanders nomination see Biden's South Carolina victory as a show of his strength as they determine who they will back?
2) Will the field narrow soon?
Yesterday, investor Tom Steyer dropped out after banking his campaign on South Carolina and failing to clear the necessary 15 per cent threshold to get delegates.
Before yesterday, Biden said that anyone who can't do well among black voters should consider dropping out. There's some history to back up that argument.
In 2016, Hillary Clinton won 89 per cent of black voters. South Carolina in particular is a good bellwether for the African American vote across the country, said Jim Kessler, a Democratic strategist with the centre-left think tank Third Way, in an email. It has a strong moderate streak and tends to have higher turnout than some of the other early nominating contests.
So what does applying that logic mean for the campaigns of Pete Buttigieg, Amy Klobuchar and Elizabeth Warren? In Nevada and now in South Carolina, they have performed poorly among voters of colour.
According to South Carolina exit polls, Klobuchar won 0 per cent of the black vote; Buttigieg 3 per cent; Warren 5 per cent. That's not an argument for being able to build a national coalition to defeat President Donald Trump.
None of them hinted they were dropping out. So the question, with Super Tuesday coming up, is if South Carolina's results prime any of these candidates to drop out later this week?
3) Will black voters propel Biden to wins elsewhere?
He launched his campaign banking on receiving the support of black voters. And in South Carolina, black voters delivered for him in big numbers. They favoured Biden over Sanders by a margin of four-to-one. Beyond South Carolina, even though Biden isn't leading national polls anymore, he remains the top candidate for black voters.
But can Biden expect black voters to vault him to the top in other states? Sanders a week ago looked like he could encroach on Biden's strength as Biden's South Carolina polling dipped and Sanders won almost a third of black voters in Nevada's caucuses. We'll find out soon if that has completely stalled out, as a slew of Super Tuesday states have large shares of black voters.
And here's someone who hasn't even been on the ballot yet and is making a big play for black voters. Speaking of ...
4) What happens when former New York mayor Mike Bloomberg is on the ballot?
On Wednesday, a new, unpredictable dynamic faces a revived Biden: Billionaire and former Republican Bloomberg will be on the ballot in all 14 states and two territories voting.
He decided to skip the first four states, which don't provide many delegates anyway, instead spending hundreds of millions of dollars, focused on the single day that will give a third of all delegates in the race. He's particularly trying to challenge Biden with black voters in Southern states with a higher percentage of black voters, like North Carolina and Georgia and Texas.
Bloomberg surged in some polling earlier this month but has since struggled in debates. But he has unlimited money, unlike Biden, and voter intrigue was high after Biden slipped in the first three contests.
5) Does Sanders have a monopoly on young voters?
Young voters form Sanders' core supporters, and always have (see his 2016 campaign). He has continued to poll strongly with them and used them to propel his early primary wins in 2020. In South Carolina, Sanders won a plurality of support from voters under 30 - but not the majority.
He won more than 40 per cent of the youngest group of voters, age 17 to 29, but Biden won votes from nearly 30 per cent of that same age group. And older millennials and Gen-Xers supported Biden over Sanders.
Biden's popularity with black voters extends to younger ones, creating an exception to Sanders' general dominance with them.
