Washington CNN  — 

Sen. Lindsey Graham says Donald Trump is a “complete idiot” and if the two face off in the Republican primary in Graham’s home state of South Carolina, “I’ll beat his brains out.”

Graham, the South Carolina senator, attacked Trump in a Tuesday morning interview on CNN.

Trump had taunted Graham earlier in the day, highlighting a poll of South Carolina GOP primary voters that showed the real estate mogul leading the pack with 30% support and Graham much further back at 4%.

“Congrats,” Trump sarcastically tweeted at Graham, noting that those four percentage points are “far better than zero nationally.”

RELATED: GOP primary poll: Donald Trump leads in South Carolina

Graham chalked Trump’s lead up to a “dark side of politics that Mr. Trump is appealing to.” He said Trump is channeling the same Republican primary voters who believe President Barack Obama is a Muslim and was born in Kenya.

“Come to South Carolina and I’ll beat his brains out,” Graham said. “I know my state. This is a silly season in politics.”

Graham launched the harshest attack yet of any of Trump’s Republican opponents, calling him a “showman” whose “policy positions are complete gibberish.”

“He is shallow, he is ill-prepared to be commander-in-chief, he doesn’t know what he is talking about in terms of how our laws work, he says the worst things possible about immigrants and women, and he’s a complete idiot when it comes to Mideast policy,” Graham said. “So I think over time, common sense will prevail.”

Trump and Graham have been sparring since the real estate mogul got into the race. Their feud boiled over most publicly when Trump revealed Graham’s personal cell phone number in a press conference, and Graham later released a video of him destroying the phone.

RELATED: Lindsey Graham: Donald Trump is a ‘jackass’