ABC News' Teddy Davis reports: Florida Republican Sen. Mel Martinez, who had previously announced that he was not going to run for re-election in 2010, has now decided to step down early. His resignation will become effective on a successor taking office to fill out the remainder of his term. In a statement to supporters, Martinez does not explain his decision to step down before completing the full six-year term to which he was elected in 2004 other than to say: "When I began my term as Senator, I promised I wouldn't simply warm a seat." Read the full statement HERE. The Martinez decision will make it possible for Florida Republican Gov. Charlie Crist to appoint a replacement to fill the remaining months of Martinez's term. Crist, who had already announced that he is running for the vacant Martinez seat, could, if he wanted to, appoint himself. Senate Republican sources say, however, that he is unlikely to make such a move since it could risk a backlash in a race that he is favored to win. Crist is instead expected to appoint a safe placeholder who won't seek the office in 2010. Two Republicans who have been floated as possible placeholders are former Florida Gov. Bob Martinez and former Florida Sen. Connie Mack. Martinez, a Cuban-American, is a former chairman of the Republican National Committee who served as Secretary of Housing and Urban Development during President George W. Bush's first term. UPDATE: As expected, Florida Republican Gov. Charlie Crist is ruling out the possibility of picking himself to fill Sen. Mel Martinez's Senate seat. Crist ruled out the possibility of picking himself in an email message to ABC News from spokeswoman Erin Isaac. As for Martinez, he said at a Friday afternoon press conference in Orlando that he is in good health and attributed his desire to quit early to a simple desire to get on with his life. "It's just my desire to move on and get on with the rest of my life," said Martinez. Martinez, who is quitting part-way through the six-year term to which he was elected in 2004, will be going to work in the private sector. The Martinez announcement comes one day after he broke with most Republicans and voted to confirm Sonia Sotomayor, a fellow Hispanic, for the U.S. Supreme Court. ABC News' Rick Klein contributed to this report.