U.S. Rep. Connie Mack will run for re-election instead of the Senate seat being vacated by Republican Mel Martinez.
Mack, whose father served two terms in the Senate, wrote to Gov. Charlie Crist on Thursday saying he won't be a Senate candidate.
Mack was among several Republicans considering the open seat. None have announced their candidacy while waiting to see if Crist seeks re-election or runs for Senate.
Mack told Crist, "I will be your strongest supporter and champion -- regardless of whether you seek re-election or election to the Senate."
Mack was elected to Congress in 2004.
Former Speaker Marco Rubio has opened a Senate exploratory committee, but has said he will wait for Crist's decision before making any campaign announcements.