South Carolina Sen. Lindsey Graham said Sunday that Trump is an "interloper and a demagogue of the greatest proportion," urging Republicans to put aside their differences and back Texas Sen. Ted Cruz for the nomination.
"The bottom line is I believe Donald Trump would be an absolute, utter disaster for the Republican Party, destroy conservatism as we know it," he said on CBS' "Face the Nation." "We would get wiped out and it would take generations to overcome a Trump candidacy."
Graham acknowledged he's had his differences with Cruz, whom he endorsed last week, many of them very public. (In February, he said: "If you killed Ted Cruz on the floor of the Senate, and the trial was in the Senate, nobody would convict you.")
"Ted Cruz, in my view, is a real Republican who I often disagree with," he said. "I'm supporting Ted because I think he's the best alternative to Donald Trump."
The senator also urged Ohio Gov. John Kasich to get out of the race or to combine forces with Cruz, saying his continued presence in the race just forces him to serve as the spoiler and could keep the party from defeating Trump.
"John, if I thought you could win, I'd be behind you because you are the most electable candidate," he said. "Work with Ted to deny Trump 1,237 ... and if you're not willing to work with Ted you're hurting the cause. By Kasich going to Utah, you're making it harder for Ted to get 50 percent."
As for the chances of actually taking down Trump, Graham pointed to the proportion of GOP voters who cast their ballots for someone other than Trump.
"Sixty-five percent of the Republican Party would like to vote for somebody other than Donald Trump," he said. "We're about to nominate the one person that not only would lose in 2016 but would destroy the party for decades to come. I'd rather lose without Trump than try to win with him. And if he wants to leave the party, leave."
Still, he would not say outright that he's willing to break the pledge he signed as a GOP candidate: to vote for the eventual nominee, whoever it is. "Ask me after the convention that question, but I'm making it pretty clear to you that I think Mr. Trump destroys the party I love," Graham said.
And in a sign of just how bad he thinks things are for his party, when Graham was asked by moderator John Dickerson whether the situation in the Middle East or the situation in the Republican Party is more complicated, Graham chose the Republican Party.
"There's a pathway forward in the Mideast--I don't see one right now for the Republican Party," he said. "...Mideast politics to me seem to be less of a mess right now than the Republican Party, and that's saying a hell of a lot."