WASHINGTON (CNN) - Florida Gov. Charlie Crist tapped Friday one of his former aides, George LeMieux, to replace retiring U.S. Sen. Mel Martinez.
LeMieux - like Crist and Martinez - is a Republican. He will serve out the remainder of Martinez's term, which expires in January 2011.
Martinez released a statement calling LeMieux a "bright, capable, and an accomplished administrator" and promised "a smooth transition."
Florida Democrats immediately blasted the pick, arguing in a statement that LeMieux's "only qualification is being Charlie Crist's crony."
"Today, Charlie Crist decided to play political games with the public's trust by appointing George LeMieux to the U.S. Senate," said Karen Thurman, chairwoman of the Florida Democratic Party.
"This glaring example of political cronyism is the last thing Florida needed while we face these tough economic times and the Congress is tackling critical issues such as health insurance reform and global warming," Thurman added.
Martinez was first elected to the Senate in 2004. He previously announced in December his intention to retire at the end of his term.
Crist, in turn, announced in May that he would not seek a second term as governor and instead would run for Martinez's seat in the 2010 election.
Three weeks ago, Martinez said he had changed his mind and decided to resign his seat as soon as a replacement could be named. He stated that he had decided to resign of his "own free will."
"There is no impending reason," he said. "It's only my desire to move on and to get on with the rest of my life."
Martinez is the only Hispanic Republican in the Senate. He recently joined eight other Republicans in voting to confirm Judge Sonia Sotomayor as the first Hispanic justice to serve on the U.S. Supreme Court.
Martinez is also one of six Republican senators who have stated they would not seek re-election next year. But the Florida senator is the second Republican who has decided to leave before the curtain drops on the 111th Congress next fall.
Sen. Kay Bailey Hutchison, R-Texas, recently announced her intention to quit the Senate three years before her term expires, in order to run for governor next year.
The five other Republicans who are retiring are Missouri Sen. Kit Bond, Kansas Sen. Sam Brownback, New Hampshire Sen. Judd Gregg, Kentucky Sen. Jim Bunning and Ohio Sen. George Voinovich.
Two Democrats will not run in 2010: Illinois Sen. Roland Burris and Delaware Sen. Ted Kaufman. The Democrats lost their filibuster-proof 60-seat Senate majority this week with the death of Massachusetts Sen. Ted Kennedy.
Republicans must defend 19 seats next year, and Democrats must protect 18.
–CNN's John King and Mark Preston contributed to this report