GettyImages-499759098
Sen. Lindsey Graham, R-S.C., speaks at the 2016 Republican Jewish Coalition Presidential Candidates Forum in Washington, Dec. 3, 2015. Getty Images

UPDATE: 10:35 a.m. EST — South Carolina Sen. Lindsey Graham, who dropped out of the Republican race for the presidential nomination last month, endorsed his one-time rival Jeb Bush Friday. Speaking at a news conference, Graham said he was impressed with the former Florida governor's performance at the sixth GOP debate Thursday night.

"He did not talk the most, but he made the most sense," Graham said. "He demonstrated somebody who, in my view, is ready on Day One to be commander in chief."

Graham applauded Bush for his stance on Muslim immigration — making sure people are "properly vetted" — and plan to combat the Islamic State group. The senator also mentioned outspoken front-runner Donald Trump by name, saying his proposal to stop Muslims from coming to the United States was the worst idea "in terms of how to fight and win this war." Graham complimented Bush's temperament and attitude.

"If Jeb Bush is president of the United States, he will put the country ahead of the party," Graham said.

Original story:

Republican presidential dropout Lindsey Graham was reportedly preparing Friday to endorse former rival Jeb Bush. Graham, a South Carolina senator, was set to announce his support for the former Florida governor at a news conference Friday morning, according to the Post and Courier. Graham was due to say that Bush's GOP nomination could mean "we will beat Hillary Clinton."

Graham ended his White House bid Dec. 21. As of Friday morning, Bush was in fifth place among Republican candidates, polling at about 5.4 percent. Billionaire Donald Trump led the pack with 37.2 percent.

Bush responded to the news Friday morning on Fox News, praising Graham for his national security and military knowledge. "His endorsement is very meaningful, and along with it comes a lot of friends and supporters of his, so I'm excited about it," Bush said, according to a transcript. "I am honored to have his support."

Many of Graham’s fans jumped to Bush after the senator left the race, including at least 10 of his campaign staff members, among them former U.S. Ambassador to Canada David Wilkins , Reuters reported last month. The senator’s support could make a difference for Bush in the important early-voting state of South Carolina, potentially giving the candidate “a shot of momentum,” according to Politico. Graham’s counterpart, Sen. Tim Scott, R-S.C., hasn’t publicly endorsed anyone yet.

Bush has the highest score among GOP candidates in FiveThirtyEight’s Endorsement Primary, with the backing of four senators and 26 representatives. But RealClear Politics data showed Bush polling at 8.5 percent in South Carolina, putting him again in fifth place.

Bush seemed to be aware of how critical the looming primaries could be for his flagging campaign, though last month he told Iowa Public Television he was optimistic.

“In Iowa, it's a question of organization. In New Hampshire, it's retail politics. In South Carolina, a great organization matters. I'm making great progress in those states, and we have the best campaign in Nevada,” he said. “So, look, in October or November, even in December of the last two election cycles, the people that were winning in December weren't the ones that ended up winning. It's just the nature of the beast, and there's no reason to rewrite history.”

Bush’s two ex-presidential relatives — his father, George H.W. Bush, and brother, George W. Bush — both won the South Carolina primaries in their campaigns.