Florida state Sen. Dan Gelber (D) will formally announce Tuesday that he will seek the Democratic nomination for the 2010 race to fill Florida's open Senate seat.

The Miami-area state legislator is expected to make his bid official after speculation that he would enter the race, the Miami Herald reported. Gelber will face off against at least one other Democratic lawmaker, Rep. Kendrick Meek, in the primary.

At least one Republican, former state House Speaker Marco Rubio, is expected to announce their intention to run.

The seat is one of several open GOP seats the Republicans will be left to defend in 2010 after Sen. Mel Martinez (R) announced his retirement.