This time, it's former Arkansas governor and presidential candidate Mike Huckabee.
"Marco believes in smaller government," Huckabee said in a release issued by the Rubio campaign. "He is a firm supporter of life. As the former Florida Speaker he was incredibly effective at bringing new ideas to the table and working to see them passed into law. He is a family man, loyal, compassionate and someone I am proud to call a friend."
Huckabee, who knows something about running against the political establishment, also took a few digs at Rubio's GOP opponent, Gov. Charlie Crist, who has been endorsed by Sen. Mel Martinez, R-Fla., and other Washington lawmakers.
"Last night, his opponent was raising money in Washington, DC," Huckabee said. "I am told he may have raised hundreds of thousands of dollars. Today, I am hoping that Marco will receive the financial support of tens of thousands of Americans; the sort who make one political contribution a year, to the candidate they believe in with their hearts not just their heads. Because I firmly believe it is these contributions that will make the difference in this race, not the money raised from lobbyists who make a new political contribution each week, betting the "smart money."
Earlier this month, Rubio also won the endorsement of Sen. James DeMint, R-S.C., one of the most conservative members of the Senate.