By Rachel Kapochunas, CQ Staff

Republican Sen. Mel Martinez of Florida said Tuesday he will not seek a second term in 2010, citing a desire to spend time with his family.

“The call to public service is strong but the call to home, family and lifelong friends is even stronger,” Martinez said at a news conference in Orlando.

Martinez said his decision “was not based on re-election prospects,” despite sagging poll numbers, and noted that he has faced difficult elections and adversity in the past. He had been expected to face a strong challenge.

Martinez is the second senator — and second Republican — to announce plans to retire at the end of the 111th Congress, which begins Jan. 6. Sam Brownback of Kansas said last year, when he dropped a nascent bid for president, that he would observe a self-imposed two-term limit.

Republicans again face the challenge of defending more Senate seats in 2010 than their Democratic counterparts, although the imbalance is not as severe as it was this year. There will be 19 GOP-held seats up for election in two years versus 17 Democratic seats, assuming Sen. Hillary Rodham Clinton , D-N.Y., is confirmed as secretary of State and resigns her seat.

Former Gov. Jeb Bush is the most prominent potential GOP candidate to succeed Martinez, but some party sources suggested he might not be interested. Other possibilities include state Attorney General Bill McCollum; former state House Speaker Marco Rubio and Rep. Adam H. Putnam , who recently stepped down as head of the House Republican Conference. Earlier in his career, Putnam said the only statewide race he was likely to consider in the future was for governor — not Senate.

McCollum, in a statement Tuesday, said, “At this point, my plan is – at the appropriate time – to announce my intention to seek re-election as Florida’s attorney general. However, given today’s development, I will seriously consider and discuss with my family a race for this U.S. Senate seat, and we will share our decision at a later date.”

On the Democratic side, Alex Sink, the state’s chief financial officer, has been mentioned as a strong potential candidate. Other possible Democratic contenders include U.S. Reps. Allen Boyd and Kendrick B. Meek , and state Sen.-elect Dan Gelber.

Florida’s senior senator, Democrat Bill Nelson , refused to discuss potential successors for Martinez on Tuesday, instead praising his GOP colleague as “a good friend, a good Senate colleague, and a good public servant.” The two senators are neighbors in the Baldwin Park neighborhood of Orlando.

Whoever runs for either party will have to raise a daunting amount of money for what is likely to be one of the next cycle’s most expensive Senate contests.

Florida is a fiercely contested battleground for the two parties. Martinez, who served as secretary of Housing and Urban Development from 2001-03, squeaked past Democrat Betty Castor and a third candidate with 49 percent of the vote in 2004.

Barack Obama carried Florida in this year’s presidential election with 51 percent. Nelson was re-elected comfortably in 2006, with 60 percent of the vote, but he won his seat in 2000 with just 51 percent of the vote.

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