In his announcement video, Harrison highlighted his birth to a 16-year-old mother, his upbringing by his grandparents, his education at Yale University and Georgetown Law School and his return to South Carolina.
The video also included clips of derogatory comments that Graham made about Trump as they both were pursuing the Republican presidential nomination in 2016, including Graham labeling Trump “a kook,” “crazy” and “not fit to be president of the United States.”
“He’s a race-baiting, xenophobic religious bigot,” Graham said in one highlighted clip.
In subsequent clips, Graham is shown saying, “No, I don’t think he’s a xenophobic, race-baiting, religious bigot,” and that Trump “deserves the Nobel Peace Prize and then some.”
“Here’s a guy who will say anything to stay in office,” Harrison said in the video. “Lindsey Graham can’t lead us any direction because he traded his moral compass for petty political gain.”
Graham, who is serving his third term, defeated his Democratic challenger in 2014 by more than 16 percentage points. Trump carried the state over Democrat Hillary Clinton in 2016 by 14 percentage points.
In an interview with The Washington Post in March, as he was considering a Senate bid, Harrison said that Graham’s reelection “is not a slam dunk for him” given his emergence as a strong Trump ally.
“The refrain these days is: What’s happened to Lindsey?” Harrison said. “He’s won in the past with a coalition of country club Republicans, independents and some moderate or conservative Democrats. But he’s lost some of those middle-of-the-road voters.”
Graham kicked off his reelection campaign in March with a visit from Vice President Pence, who emphasized Graham’s loyalty to Trump.
Following Harrison’s announcement Wednesday, the National Republican Senatorial Committee sought to downplay his prospects.
“Harrison is a looney liberal who was hand-picked to run by radical Washington Democrats,” said NRSC spokesman Nathan Brand. “Lindsey Graham is one of the most popular U.S. Senators in the country because South Carolina voters know that he has delivered results and has been a tireless fighter for Palmetto State values.”
Robert Costa contributed to this report.