"Some of you may know that I have a television show," Colbert said to cheers from the audience. "And not only am I Stephen Colbert, but I play one on TV."
"I have never actually supported any candidate before," Colbert went on to say. "But I can wholeheartedly support [my sister]."
Colbert-Busch is running for her state's Democratic party nomination in the special election to replace Sen. Tim Scott, who left his House seat for the Senate in December. Should she receive her party's nomination, Colbert-Busch faces a tough campaign in the heavily red state.
Colbert first mentioned his sister's campaign on his show earlier this month, though he joked he was leaning towards her Republican opponents.