Martinez, former secretary of Housing and Urban Development, has formally entered the race for the Republican nomination for the seat being vacated by Democratic Senator Bob Graham.
Harris, now a congresswoman representing Sarasota, Fla., has been noncommittal on whether she will run for the Senate.
When reached Tuesday, Harris campaign director Jessica Furst offered only a seven-word replay.
"She has made no decision quite yet," Furst said.
But she leads in recent polls anyway.
Harris became the darling of the Republicans and the archenemy of the Democrats when, as secretary of state and chief elections officer, she was at the center of Florida's vote counting debacle in the 2000 presidential election.
Bush won Florida by 537 votes, after the Supreme Court canceled a recount, and thereby gained the presidency.