Barry M. Seltzer, 46, was taken into custody at his home and charged with aggravated assault with a deadly weapon, the Sarasota Herald Tribune reported.
A police report said Harris and a group of supporters were campaigning on the corner on an intersection about 6 p.m. when they saw the Cadillac.
Police said the car drove up the sidewalk directly at Harris, a former secretary of state and major figure in the post-election dispute between President Bush and former Vice President Al Gore.
The arrest report quoted Seltzer as telling officers: "I was exercising my political expression. I did not run them down, I scared them a little."
Harris said she was afraid for her life.
Seltzer, a landlord for several rental properties, was taken to the Sarasota County Jail.
Harris is running for re-election against Democrat Jan Schneider in Tuesday's general election.