The write-in candidate's name is Percy, and he's a border collie-German shepherd mix of undetermined age.
"No one has a realistic expectation that a dog can get elected," said owner Wayne Guentner. "But plenty of people will be willing to vote for a dog to represent their discontent with the political system."
Although the campaign is clearly labeled as a satirical parody, Guentner said 5 percent of the vote would be a victory for Percy.
Harris, Percy and six others are running for an open seat in a safe Republican district in Sarasota County.
Harris has raised $1.7 million, and analysts in both parties say there is almost no chance she can lose.
But still Percy continues to campaign. He has a Web site featuring a profile by campaign member Pam Marwede.
"Although he takes a hard line with social parasites, especially fleas and worms, he has always had a compassion for those less fortunate," the profile says. "Indeed Percy, too, was once homeless, a disadvantaged runaway."
Harris is playing along with the gag and says his bark is worse than his bite.
Campaign spokeswoman Jessica Furst says Percy "has a lot of paws to shake to catch up."