A 2010 cycle that looks to contain more of the same for reeling Senate Republicans got off to an ominous start Tuesday, with the unexpected announcement that Sen. Mel Martinez (R-Fla.) will not seek reelection.

It’s not clear whether Martinez’s retirement leaves the GOP better or worse off in Florida — he was an incumbent, but he suffered from poor approval ratings and already faced a treacherous reelection race.

For a Democratic Party aiming for 60 seats-plus, things are heading in the right direction: Martinez is the second GOP senator to step aside for the 2010 cycle, joining Sen. Sam Brownback (Kan.).

Brownback’s seat appears to be less likely to switch from red to blue, but Democrats have been closely contesting races in other deeply red states. They could make the Kansas race instantly competitive with Gov. Kathleen Sebelius (D), who remains a term-limited free agent without an appointment, thus far, to the Obama administration.

The GOP also has to deal with more seats to defend (19) than Democrats (16) and a less appealing target list.

When the 111th Congress begins, four of the five oldest GOP members will be facing reelection. Most of them have already insisted they are running, but questions remain about some of them.

Sen. Jim Bunning (R-Ky.), who is 77, has said he will run and needs $10 million to win in 2010, but he had banked a miniscule $175,000 for the race as of Sept. 30.

Sen. Arlen Specter (R-Pa.), at 78, has been adamant that he will run, but he appears set for an arduous primary and general election, both of which he already faced in 2004.

Sen. Richard Shelby (R-Ala.), who is 74, has said he plans to seek reelection, but that was the same thing Martinez was saying as late as two weeks ago.

The GOP also could have to deal with otherwise safe seats held by 75-year-old Sens. Bob Bennett (R-Utah) and Chuck Grassley (R-Iowa), should they retire.

In announcing his retirement Tuesday, the 62-year-old Martinez passed on what was set to be one of the most difficult reelection battles in the country.

Though the race might be no less winnable with him out, recruiting for it will be an early challenge for incoming National Republican Senatorial Committee Chairman John Cornyn (Texas).

A source close to Cornyn said the situation doesn’t change the committee’s outlook on Florida, which the source maintained is a GOP-leaning state with a strong bench.

“That being said, it’s going to be a tough fight, particularly in the current political environment,” the source added.

Florida political insiders say there are two particularly prominent and likely names to run for Martinez’s seat: Alex Sink, the state’s Democratic chief financial officer, and Marco Rubio, the charismatic former GOP state House Speaker.

Elected in 2006, Sink has often been mentioned as a potential candidate for governor or Senate. Currently the highest-ranking Democrat in state government, she has said publicly that she plans to decide her political future “very soon.”

Sources said Tuesday that she was planning to announce that she would seek reelection to her current post on the assumption that both Martinez and Gov. Charlie Crist (R) were staying put, but Martinez’s decision caused her to reconsider and delay.