Sen. Lindsey Graham (R-SC) on Sunday said President Donald Trump could be the first president to “go down” as a result of his inability to stop tweeting about the investigations he appears to view as a threat.

“You may be the first president in history to go down because you can’t stop inappropriately talking about an investigation that, if you just were quiet, would clear you,” Graham said on CBS’ “Face the Nation.”

He said Trump’s tweeting is a source of frustration for Republicans.

“This is not helping,” Graham said.

Trump nevertheless began Sunday with one of his by-now regular Twitter salvos at Democrats and fired FBI Director James Comey.