In one of the country's more unusual political protests, Percy, a border-collie mixed breed, will be Ms Harris's opponent in the Republican race to obtain a seat in the US House of Representatives - the lower house of Congress.
Ms Harris is perhaps best known as one of the key players in the controversial US presidential elections in 2000.
The vote in Florida proved crucial to the election outcome that eventually put George W Bush in the White House.
Percy's owner, charter boat captain Wayne Genthner, said he wants to highlight the injustices of campaign finance in the US political system. He says it is a process that excludes most ordinary people.
"We hope by running a canine against a nationally known political person we can draw attention to voter disenfranchisement and disconnection," he told Reuters news agency.
Meeting the public
Acting as campaign manager to his canine candidate, Mr Genthner and his volunteer staff have already been out on the streets meeting potential voters, shaking hands - or paws - and handing out flyers and stickers.
Popular slogans have included "Never made a mess in the House, never will," and "Percy - putting the 'lick' back into Republican", the Associated Press news agency reported.
Mr Genthner says that Percy is a compassionate conservative who is tough on crime - "he will personally chase down any criminal he sees", and social parasites, especially fleas and worms.
His supporters also need not fear any potentially embarrassing sex scandals, as Percy has been neutered.
Good-natured
So far, Mr Genthner has spent about $600 on his campaign, in contrast to the estimated $1.7m Ms Harris has raised so far to run for the seat.
However, Ms Harris's campaign office has, so far, been good-natured about Percy's challenge, not least because it is widely expected that she will succeed in her bid.
"Percy the dog has a lot of paws to shake to catch up with our grass roots effort and huge volunteer base," Jessica Furst, Ms Harris's campaign spokeswoman said.