“It’s hard to construct a scenario where South Carolina is not the gateway to the nomination,” said David Plouffe, former President Barack Obama’s 2008 campaign manager, describing it as a springboard into the most delegate-rich day of the primary and a proving ground for who can appeal to black voters. “If you don’t have the capacity to perform well in South Carolina, it likely means you’re not capable of performing well later in the primary.”

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This state is poised to play an outsized role in 2020 because of a confluence of demography and timing. South Carolina will be the first contest in which a majority of those casting ballots will be African-American. In 2016, black voters made up roughly 60 percent of the South Carolina Democratic primary vote. (In the general election, they usually make up less than a quarter of the vote in a state that is reliably Republican.)

The winner here will enter the March 3 Super Tuesday contests with a burst of momentum. South Carolina will mark the final clash before California, Texas and an array of similarly diverse states, comprising over 30 percent of the race’s total delegates, vote just three days later.

While some of the nine Super Tuesday states allow early balloting, the Democrats who wait to vote on Primary Day itself will be heavily influenced by the South Carolina results.

“People ask me if I’m concerned California has moved up, and I say: No, it just makes South Carolina more important, because all that people are going to be talking about on Saturday night, Sunday and Monday is who won South Carolina,” said Jaime Harrison, a former state chairman here, referring to California’s decision to move its primary from June to March.