The 2004 United States Senate election in Florida took place on November 2, 2004, alongside other elections to the United States Senate in other states as well as elections to the United States House of Representatives and various state and local elections. Incumbent Democratic U.S. Senator Bob Graham decided to retire instead of seeking a fourth term. Graham made an unsuccessful bid for the Democratic presidential nomination. The primary elections were held on August 31, 2004. Republican Mel Martínez won the open seat with 49.4% of the vote to Democratic nominee Betty Castor's 48.3%. With a margin of 1.1%, this election was the closest race of the 2004 Senate election cycle. This was the first open-seat United States Senate election in Florida for this seat since 1974.

Democratic primary

Candidates

Results

Republican primary

Martínez was supported by the Bush Administration.

Candidates

Results

General election

Candidates

Predictions

Polling

Graphical summary

Results

Counties that flipped from Democratic to Republican