Florida Republican Marco Rubio, a former state House Speaker, announced Tuesday that he is a candidate for the U.S. Senate seat of retiring one-term Republican Mel Martinez .

Rubio’s announcement pre-empted a highly anticipated decision by Republican Gov. Charlie Crist , who is expected to reveal within days whether he will run for a second term as the state’s chief executive in 2010 or instead bid for the Senate seat.

In an announcement video posted on his Web site, Rubio criticized political leaders in Washington, D.C., as supporting larger government and increased spending.

“The majority of us don’t agree with that view, and we deserve a voice in American politics. And that’s why I want to serve in the United States Senate, because I want to be a part of offering an alternative,” Rubio said.

Rubio alluded to Crist in his announcement, stating, “I’m under no illusions about how difficult this will be. I know that there are people more famous than I who may enter this race.”

Rubio’s entry defied the conventional wisdom that the field for the Senate contest was frozen pending Crist’s decision, and that other Republicans would defer to Crist if he decided to enter that race.

Crist, who has had strong approval ratings since his election as governor in 2006, has said consistently that he will not publicly state a decision about his 2010 plans until after the Florida legislature adjourns its annual session. That adjournment is now expected to occur on May 8.

It is no secret that Crist is pondering which office to pursue next year. He emerged as the most prominent potential Republican Senate candidate since January, when former Gov. Jeb Bush — regarded by many Republicans as their “dream” Senate candidate — stated that he would not run.

His backers say his popularity would give the GOP a leg up on holding a seat that the slumping national party needs to win avoid slipping deeper into the minority in the chamber.

Rubio was not deterred by the possibility of a Crist bid for the Senate.

Like the outgoing incumbent, Rubio is a prominent member of Florida’s politically potent Cuban-American constituency.

Seen by a number of Republicans as a rising star in the party, Rubio was elected to the state House from a Miami district in 2000 when he was 28 years old, and served as Speaker from 2006 to 2008 while in his mid-30s.

Rubio will turn 38 on May 28; Crist, who formerly served in the state Senate and as state education commissioner and Attorney General, will turn 53 on July 24.