At the same time, opponents of legalization are talking with voters and lawmakers about the dangers of marijuana use, the impact on children and public safety. Further, they say legalization would undo decades of substance-abuse education.

Arizonans for Responsible Drug Policy, Maricopa County Attorney Bill Montgomery and others are urging the public to learn about marijuana legalization's impact in Colorado, pointing to increased marijuana use by children, concerns over impaired drivers and drug-related expulsions from schools.

Seth Leibsohn, chair of Arizonans for Responsible Drug Policy, called the billboard a "stunt, hijacking a laudable and charitable sports tournament" to promote substance abuse.

"Using the laudable and charitable Waste Management Phoenix Open golf tournament as a springboard to publicize a political campaign to legalize marijuana in Arizona is the opposite of good health, good education and good public policy -- and certainly the opposite of good taste," Leibsohn wrote in a statement to The Arizona Republic....