The proposition was sponsored by Arizonans for Humane Farms, a coalition of animal welfare organizations, including the Arizona Humane Society, the Humane Society of the United States, the Farm Sanctuary, and the Animal Defense League of Arizona. It was opposed by the Campaign for Arizona Farmers and Ranchers with funding from agribusiness proponents such as the American Veal Association, the National Pork Producers Council, the AZ Cattle Feeders Association, AZ Pork Council, American Farm Bureau Federation, AZ Farm Bureau Federation, AZ Cattleman's Association, and the United Dairymen of Arizona.
The chairperson of the Yes on Proposition 204 campaign was Cheryl Naumann , president and CEO of the Arizona Humane Society. Another spokesperson was Maricopa County Sheriff Joe Arpaio, and the campaign was also endorsed by radio legend Paul Harvey. More than 200,000 Arizonans signed petitions to place the measure on the ballot. More than 100 Arizona veterinarians endorsed Proposition 204.
The opposition to Proposition 204 argued that the primary organizers of the measure are anti-meat groups and that a similar measure passed in 2002 in Florida led to bankruptcies of one farm in the state. However, the Florida Farm Bureau explicitly denies the claim that any farms went out of business as a result of the 2002 ballot measure in that state. In an article published the week after the 2002 election, a Florida Farm Bureau spokesman denied this claim, stating that "It's because of low prices, not the amendment." However, in an article the following month in the St. Petersburg Times one of the two Florida hog farmers covered under Proposition 204 stated that he had slaughtered all of his sows because of the expense of complying with it.
Prop 204 was endorsed by the Arizona Republic the Arizona Daily Star , the East Valley Tribune the Scottsdale Tribune, the Northwest Explorer , and the Tucson Weekly.