Graham has won a fourth six-year term in the US Senate in the 2020 elections, according to analysts with the Associated Press.
News of his victory comes shortly after Sen. Mitch McConnell (R-KY), who leads Republicans in the Senate, was also declared to be the winner of his reelection race.
Like McConnell, Graham faced a tough opponent with deep pockets as Democrats rallied to try and oust one of the Senate's most powerful conservatives.
Democrat Jaime Harrison raised a record-breaking $57 million in campaign funds during the final quarter prior to the election, according to the New York Times, which reported his average donation was $37. Overall, Harrison raised more than $100 million during the race. However, before it was all over, Graham said he had also solicited more than $100 million, taking in $1 million a day in the first two weeks of October.
"This is the biggest challenge that I have ever faced,” Graham told AP on Tuesday evening.
Once a fierce critic of US President Donald Trump, Graham fell in behind the Republican president after his 2017 inauguration, even if Trump hasn't quite repaid him the favor.