Because this state's presidential primaries are the first in the southeastern United States, experts say they are among the most important early battlegrounds in the nominee selection process.
For weeks, Republican and Democratic candidates have crisscrossed the state. From major rallies packing thousands of supporters into convention centers and town halls to smaller discussions in churches and university buildings, candidates on both sides of the aisle have fought hard for each vote in this pivotal state.
Spread out over two weeks, the campaigning ends Saturday when Democratic Party voters go to the polls to choose between Hillary Clinton and Bernie Sanders.
For the Democrats, one key demographic will go a long way in determining who is better suited to represent their party.
"The South Carolina Democratic primary is going to be over half African-American," said Scott Huffmon, a political science professor at Winthrop University in Rock Hill, South Carolina. "This is the first test of black support. And of course, African-Americans vote over 90 percent for the Democratic Party, so knowing who is the favorite for this core constituency is really important for the Democrats."
Based on opinion polls, that candidate is Clinton. To bolster her support among African-Americans, she hosted an emotional forum Tuesday at a Baptist church in Columbia with mothers who have lost children to gun violence – including the mother of Trayvon Martin, the Florida teen who was shot and killed by a neighborhood watch coordinator.
Sybrina Fulton, Martin's mother, was clear about whom she supported: "We have an opportunity to have someone who is going to stand up for us as African-Americans, for us as women. I say my vote goes to Hillary Clinton."
Other members of Clinton's forum included the mother of Eric Garner, who was choked to death while in police custody, and former U.S. Representative Gabrielle Giffords, who was shot while meeting with her constituents in Arizona.
While Clinton has ramped up events like this across South Carolina, Sanders, who trails heavily in early polling, has chosen to campaign in other states. He is expected to return to South Carolina on Friday, the day before the primary.
Some observers have said this is a sign Sanders has conceded defeat in the state; Sanders has denied this.
As for the Republicans, Huffmon said Trump's win in South Carolina last Saturday showed he can appeal to different types of conservatives – and also was important for strategic reasons.
"If you are the type of candidate who can appeal to the electorate of South Carolina, you're the type of candidate who can appeal to the entire South, and that's really important for the Republicans," Huffmon said.
For Republicans, South Carolina is vital. It's the first state where support among different types of conservatives can be truly measured. Since 1980, every Republican who has won South Carolina has gone on to win the nomination – until Newt Gingrich won the state in 2012, beating out eventual nominee Mitt Romney.
Some analysts believed this was the end of South Carolina’s predictive ability, but Huffmon said he thought the state in 2012 was the "canary in the coal mine," foretelling the rise of anti-establishment, insurgent candidates like Trump and Ted Cruz.
Many analysts like Huffmon agree it's not yet inevitable that Trump will win the Republican nomination, with Marco Rubio building establishment support and Cruz remaining a contender. But Huffmon said, "The more Trump wins in these earlier contests, the more likely it becomes."
WATCH: Hillary Clinton Addresses a Town Hall in South Carolina