Sen. Lindsey Graham (R-S.C.) warned at a political gathering in his home state Monday that there “could be a war within the Republican Party” over President Donald Trump’s border wall.

But he also threatened those who turn their backs on the president.

His “war” remarks to reporters at the First Monday GOP club in Greenville apparently referred to the possible reaction if Trump declares a national emergency to get his wall built.

“It seems to me that [Trump] is going to have to go it alone,” conceded Graham, who said he “isn’t very optimistic” legislators will work out a funding deal.