(CBS) — It all started years ago, during the push for then-President Bill Clinton’s impeachment, when Lindsey Graham, then a House member, was presenting the case to senators, including Arizona’s Sen. John McCain.

“Congressman Graham, on the most solemn occasion, said, ‘You know, where I come from, any man calling a woman at 2 a.m. is up to no good,'” McCain said in March of 2017, explaining the history of their friendship on CNN. “I knew right then that Lindsey Graham was a guy I wanted to spend time with.”

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It was a friendship that would remain strong to the very end. McCain died on Saturday at 81.

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“America and Freedom have lost one of her greatest champions,” Graham tweeted Saturday night. “….And I’ve lost one of my dearest friends and mentor.”

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“I will need some time to absorb this, but I want Cindy —and the entire McCain family — to know they are in my prayers.”