Senator Lindsey Graham (R., S.C.) will win reelection to a fourth term, the Associated Press has declared.The victory for Graham comes after speculation that Democratic challenger Jaime Harrison might have been able to pull off an upset win. Harrison raised almost $50 million in the third quarter and was tied with Graham in polls in October, but in recent days Graham pulled ahead in polling."To the pollsters out there: you have no idea what you're doing," Graham said during his victory speech. "And to all of the liberals in California and New York, you wasted a lot of money. This is the worst return on investment in the history of American politics."Originally skeptical of Donald Trump, Graham has become one of the president's closest allies in the Senate. As head of the Senate Judiciary Committee, Graham is currently leading an investigation into the origins of the Russia probe of the 2016 Trump campaign.Graham's victory offers some reassurance to Republicans who feared they would lose control of the Senate. Republicans currently hold a slim majority of 53–47, and Democrats have mounted strong challenges to incumbent Republican senators Susan Collins (R., Maine), Thom Tillis (R., N.C.), and Graham himself.Additionally, Colorado Republican Cory Gardner has lost his Senate race against former governor John Hickenlooper.Graham's state of South Carolina was also called for Trump earlier on Tuesday night. While Harrison's challenge to Graham had heightened Republican concerns about South Carolina, the traditionally Republican state will contribute its nine electoral votes for Trump.