By Rachel Kapochunas, CQ Staff

Republican Sen. Mel Martinez on Tuesday made a very early announcement that he will not seek re-election in 2010. And the nascent open-seat race has drawn interest from numerous potential candidates in his home state of Florida, frequently a hotbed of partisan competition.

But maneuvering among many would-be contenders awaits word from two political stars — Republican Jeb Bush, the former governor, and Democrat Alex Sink, the state’s chief financial officer — who have unique potential to emerge as their parties’ strong front-runners.

Marco Rubio, a Republican who formerly served as state House Speaker, is in the top tier of possible GOP candidates for the open Senate seat. But he told CQ Politics Wednesday that he would defer to Bush, describing him as the best candidate for the job. “If he runs, I think all of us should get behind his efforts,” Rubio said. Rubio added he would consider running for Senate if Bush — who served the state limit of two terms as governor, from 1999 to 2007 — were to decide not to enter the race.

Connie Mack , just elected to his third term representing the 14th Congressional District in southwestern Florida, is another potential candidate who on Wednesday stated his support for Bush.

“Jeb Bush has a proven track record of leadership that would once again benefit the people of Florida, and indeed the entire nation. He would make an outstanding United States senator,” Mack said in a statement.

Democrats, meanwhile, touted Sink — whose office is analogous to treasurer in most states — as a potential Senate candidate even before Martinez announced he is stepping aside.

Democratic state Sen. Dave Aronberg, mentioned as a possible candidate, told CQ Politics Wednesday that entering the Senate race is “unlikely” for him and he has not given it “much thought.” He also revealed his support for Sink, noting her positioning as a Democratic moderate and the successful statewide campaign she ran in 2006, even as Charlie Crist was winning for governor at the top of the Republican ticket.

“Alex Sink would make a great U.S. senator, and I think if she runs she would win,” Aronberg said.

Despite her prominence in state politics, Sink would have a hard time matching the enviable statewide name recognition Bush would bring to a Senate race. Bush was first elected governor in 1998 — the same year that his brother, George W. Bush , was re-elected as governor of Texas, a prelude to his 2000 win for his first term as president. Jeb Bush was re-elected governor in 2002. And unlike the president, who saw his poll numbers plummet during his second term in the White House, Florida’s Bush enjoyed strong job approval ratings throughout his tenure as governor.

But there are some reasons to doubt whether Bush would jump into the Senate contest. Republicans in the state previously indicated they believed Bush held little interest in being a senator. Despite his personal popularity, he might have to deal with “Bush fatigue,” as George W. Bush ’s unpopularity contributed greatly to Democrat Barack Obama ’s presidential victories nationally and in Florida. The nation’s economic downturn might also cause some uncomfortable questions for the former Florida governor, as he was hired in August 2007 as an advisor to Lehman Brothers, the now-defunct Wall Street private equity firm.

When asked about a Bush candidacy, Republican Gov. Charlie Crist told reporters Wednesday, “We’ll see what develops. I imagine a lot of people will have interest. Time will tell. These things usually take a little while to sort of sort out. He’s a great Floridian.” Crist won the 2006 open-seat election to succeed Bush as governor.

Waiting in the Wings

There is no shortage of fall-back options for either party should Bush or Sink or both decide not to run for the Senate.