Longtime South Carolina Republican Senator Lindsey Graham is getting a challenger in the 2020 senate race as former senior Democratic National Committee official Jaime Harrison says he's "ready to fight for a better future."

"Lindsey Graham's story is just comical," Harrison, the former chairman of the South Carolina Democratic Party, says in his first campaign ad. Harrison also knocks Graham for his loyalty to the president despite publicly lambasting then-candidate Donald Trump in 2016 as a "race baiting, xenophobic and religious bigot." Harrison suggested Graham would say "anything to stay in office" and has "traded in his moral compass for petty political gain."

Harrison told MSNBC's Rachel Maddow on Tuesday that Graham's decision to change his tune on President Trump could cost him support among Republicans and deliver crossover votes to his Democratic challenger.

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"What we are seeing with Lindsey Graham right now, it makes you question his character. I used to think this was a guy who was a statesman, a guy who could stand above the fray and help solve the issues...but he's a chameleon that's changed his colors."

Harrison, however, faces an uphill battle against Graham, who was first elected to the seat in 2002. The Republican remains relatively popular in the overwhelmingly red state as he continues to serve as one of the president's staunchest allies in Congress. Mr. Trump secured the state by 14 points in the 2016 election and South Carolina has not elected a Democrat to the Senate since 1998, when the late Sen. Fritz Hollings won re-election.

While aware of the "ruby red" color of his home state, Harrison argued that the South is on the "verge of a renaissance" for Democrats. He pointed to African American Democrats such as Georgia's Stacey Abrams and Florida's Andrew Gillum, who both narrowly lost races for statewide office last year.

"We really are on the verge of changing something and we've seen it even with recent elections in South Carolina -- we picked up a congressional seat, we picked up a state senate seat, we picked up a number of House seats when pundits thought we didn't have a shot...it's all about investing and fighting," Harrison, who is also African American, told Maddow.

The National Republican Senate Committee, meanwhile, slammed Harrison as a "looney liberal."

"Harrison is a looney liberal who was hand-picked to run by radical Washington Democrats," NRSC spokesperson Nathan Brand told CBS News. "Lindsey Graham is one of the most popular U.S. Senators in the country because South Carolina voters know that has delivered results and has been a tireless fighter for Palmetto State values."

Fellow Republican and South Carolinian Sen. Tim Scott was also confident in Graham's 2020 campaign, telling CBS News on Wednesday: "I look forward to Senator Graham's reelection, and continuing to serve South Carolinians alongside him in the U.S. Senate."

Harrison often cites his humble beginnings. His mother dropped out of high school, and he was raised by his grandparents in rural Orangerburg, where he says they "made do with the opportunities we created for ourselves." Harrison went on to study at Yale University and Georgetown Law.

The Democrat previously worked at the Podesta Group, a lobbying group. He was also an adviser to Rep. James Clyburn, where he became the youngest person and first African American to serve as executive director of the House Democratic Caucus.

Harrison ran for DNC chairman in 2017. He later left the race and endorsed current Democratic chief Tom Perez, and now serves as the associate chair and senior counselor for the group.