Graham, who supported Jeb Bush’s now-defunct campaign, said he is backing Cruz because Trump’s other rival — Ohio Gov. John Kasich — does not have a path to the nomination.
“I prefer John Kasich; Cruz is not my first pick by any choice,” Graham said. “But I don’t see how John Kasich can mount the opposition that Ted Cruz can to stop Donald Trump from getting 1,237” — the number of delegates needed to secure the nomination.
Sen. Mike Lee (R-Utah) last week became Cruz’s first Senate endorsement, a sign of the Texas senator’s persistent unpopularity among his colleagues.
Cruz has worn this outsider status as a badge of honor on the campaign trail, saying he wants to take on the “Washington cartel.”
Asked if Cruz welcomed his endorsement, Graham said: “He certainly welcomes my effort to raise money, and in the pro-Israel community, I think I have some resonance. I’ve sort of dedicated my public life to national security. I’m seen as a strong supporter of Israel, I’m proud of that fact, and Ted has been great on Israel.”
Cruz will speak at the American Israel Public Affairs Committee Policy Conference on Monday in Washington, D.C. According to CNN, Graham will host a fundraiser for Cruz that day on the sidelines of the event.
Cruz spokeswoman Catherine Frazier said the campaign is “thrilled” by Graham’s endorsement, saying it indicates that Republicans realize “if we do not defeat Trump in this primary we will have a Democrat as the next president.”
Former GOP presidential candidate Marco Rubio on Wednesday called Cruz “the only true conservative left in the race,” a sign he could be leaning toward endorsing Cruz.
But it is unclear whether Graham’s announcement will bring more establishment GOP lawmakers to Cruz’s side.
Graham, who withdrew from the presidential primary in December, has been consistently critical of Cruz and made it clear in January he wasn’t thrilled about the idea of having to choose between Cruz and Trump.
“If you nominate Trump and Cruz I think you get the same outcome,” Graham told reporters Jan. 21. “Whether it’s death by being shot or poisoning, does it really matter?”
Graham has a history of negative comments about Cruz. “If you killed Ted Cruz on the floor of the Senate, and the trial was in the Senate, nobody would convict you,” he joked Feb. 26.
The same day, he suggested Cruz and Trump were both liars. “I was asked the hardest question in my political life: ‘Do you agree with Donald Trump that Ted Cruz is the biggest liar in politics?’” he said. “Too close to call.”
Graham on Thursday acknowledged his about-face.
“This an odd moment, I’ll be first to say,” he told reporters.
“We started out trying to nominate somebody to run in 2016; now I find myself having to fight for the heart and soul of the Republican Party,” Graham said. “I think if we nominate Donald Trump, then we put at risk the heart and soul of conservatism.”
Katie Zezima contributed to this story.