Graham says in a statement Friday he "cannot in good conscience support Donald Trump because I do not believe he is a reliable Republican conservative nor has he displayed the judgment and temperament to serve as Commander in Chief."
South Carolina's senior senator also says he will join a growing list of veteran Republicans, including both Presidents Bush, Mitt Romney, John McCain and others, now declining to attend the party's convention this summer in Cleveland, Ohio.
"He's a race-baiting, xenophobic, religious bigot," Graham told CNN late last year.