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, elections to the United States House of Representatives, and various state and local elections. Democratic incumbent Bob Graham ran unsuccessfully for president of the United States instead of seeking a fourth term. Mel Martínez won the open race to succeed Graham over Betty Castor.
Primary elections were held on August 31, 2004. Castor defeated U.S. representative Peter Deutsch to win the Democratic nomination, while Martínez won the Republican nomination over 2000 nominee Bill McCollum and businessman Doug Gallagher with the support of President George W. Bush.
In the general election, Martínez won the open seat with 49.4 percent of the vote to 48.3 percent for Castor. This was the first open election for this seat since 1974 and the closest race of the 2004 United States Senate elections. As of 2026, this is the last election in which an incumbent senator opted not to run for re-election in Florida.
Democratic primary
Candidates
- Betty Castor, former president of the University of South Florida, former education commissioner of Florida, and former state senator
- Peter Deutsch, U.S. representative from Broward County
- Bernard Klein, businessman
- Alex Penelas, mayor of Miami-Dade County
Declined
- Bob Graham, incumbent U.S. senator since 1987 and former governor
Republican primary
Candidates
- Johnnie Byrd, state representative from Plant City and speaker of the Florida House of Representatives
- Doug Gallagher, businessman
- Larry Klayman, attorney
- William Kogut
- Sonya March
- Mel Martínez, former U.S. secretary of Housing and Urban Development and candidate for lieutenant governor in 1994
- Bill McCollum, former U.S. representative from Longwood and nominee for U.S. Senate in 2000
- Karen Saull
Withdrew
- Mark Foley, U.S. representative from Jupiter (withdrew September 6, 2003)
- Daniel Webster, state senator from Clermont
- Dave Weldon, U.S. representative from Indialantic
Campaign
An early contender for the Republican nomination was U.S. Representative Mark Foley, who raised $3 million for his Senate campaign and was seen as marginally more moderate than his opponents. However, longstanding rumors regarding Foley's sexuality came under scrutiny in the alternative press. While Foley denounced the rumors in an unusual press conference, he did not deny them, instead arguing that his sexuality had no bearing on his ability as a legislator. Foley withdrew from the campaign on September 6, 2003, citing his father's diagnosis with cancer. Foley would later resign from office in 2006 and come out as "a gay man" after revelations that he had sent explicit sexual messages to teenage boys who had served as congressional pages.
Martínez was supported by the Bush administration.
General election
Candidates
- Dennis Bradley, activist (Veterans)
- Betty Castor, former president of the University of South Florida, former education commissioner of Florida, and former state senator (Democratic)
- Mel Martínez, former U.S. secretary of Housing and Urban Development and candidate for lieutenant governor in 1994 (Republican)
Endorsements
Betty Castor (D)
Mel Martínez (R)
Results
Results by county
Counties that flipped from Democratic to Republican
- Calhoun (largest city: Blountstown)
- Citrus (largest city: Homosassa Springs)
- Dixie (largest city: Cross City)
- Glades (largest city: Moore Haven)
- Gulf (largest city: Port St. Joe)
- Levy (largest city: Williston)
- Putnam (largest city: Palatka)
- Taylor (largest city: Perry)
- Jackson (largest city: Marianna)
- Lafayette (largest city: Mayo)
- Union (largest city: Lake Butler)
- Washington (largest city: Chipley)
- Brevard (largest municipality: Palm Bay)
- Okeechobee (largest municipality: Okeechobee)
- Polk (largest municipality: Lakeland)
- Miami-Dade (largest city: Miami)
- Osceola (largest municipality: Kissimmee)
- Orange (largest city: Orlando)
- Escambia (largest city: Pensacola)
- Hendry (largest city: Clewiston)
- Marion (largest city: Ocala)
- Hardee (largest city: Wachula)
- Highlands (largest city: Sebring)
- Indian River (largest city: Sebastian)
- Lake (largest city: Clermont)
- Lee (largest city: Cape Coral)
- Suwannee (largest city: Live Oak)
- Duval (largest municipality: Jacksonville)
- Charlotte (largest city: Charlotte)
- Columbia (largest city: Lake City)
- DeSoto (largest city: Arcadia)
- Gilchrist (largest city: Trenton)
- Sumter (largest city: The Villages)
- Bradford (largest city: Starke)
- Baker (largest city: Macclenny)
- Bay (largest city: Panama City)
- Clay (largest city: Lakeside)
- Holmes (largest city: Bonifay)
- Manatee (largest city: Bradenton)
- Martin (largest city: Palm City)
- Nassau (largest city: Yulee)
- St. Johns (largest city: St. Johns)
- Walton (largest city: Miramar Beach)
- Seminole (largest municipality: Sanford)