The State, two dozen former financiers of Graham have jumped ship to back Harrison. The Democrat outraised Graham by more than $1 million in the first three months of 2020, joining a swath of challengers in key Senate races who have hauled in more cash than Republican incumbents so far this year.

Another good sign for Harrison is that the South is a region that's becoming more diverse, with more African American and Latino voters. While white residents still make up about 64 percent of South Carolina's population, the number of registered nonwhite voters surpassed 1 million for the first time in the state's history earlier this year. Harrison said he's working to build a broader coalition of voters than candidates before him.

"I'm talking about their aspirations, their hopes, their dreams and their fears--and doing it in such a way where they see a path forward. It's something Graham has not been able to do," Harrison said.

There's some proof he may be right. The most recent polling shows him and Graham tied at 42 percent support among registered voters.