Story highlights Lindsey Graham is the senior senator from South Carolina and is a former Republican presidential candidate

He plans to make his Jeb Bush endorsement announcement Friday morning in Charleston

North Charleston, South Carolina (CNN) Former Republican presidential candidate and South Carolina Sen. Lindsey Graham endorsed Jeb Bush for president, saying he believes the former Florida governor has the backs of America's troops.

"I have concluded without any hesitation, without any doubt that Jeb Bush is ready on day one to be a commander in chief worthy of the sacrifices of the one percent fighting this war," Graham said from a North Charleston hotel Friday morning, with Bush at his side.

The senior senator from the Palmetto State also explained why he didn't back fellow senator and outspoken defense hawk Marco Rubio.

"I think Marco Rubio will be president of the United States one day. I think he's one of the most gifted people I've ever met. I like him. But I wasn't ready to be president at 44," Graham said, stressing the important of experience.

Bush and Graham have had a good relationship throughout the campaign and have frequently discussed policy behind the scenes. The two were seen having drinks at a Manchester hotel just three days before Graham announced he was dropping out.

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