California voters will decide this November whether to legalize marijuana for recreational use.
Supporters gathered enough signatures to put the issue on the ballot.
"The tide has turned," said Dan Newman, a strategist with the campaign backing the measure. "The combination of the broken budget and dysfunctional cannabis laws have created the perfect storm for this initiative to pass in November."
California was the first state to legalize medicinal marijuana in 1996. Since then, 14 states have followed California's lead.
The new initiative would allow adults to possess enough pot to roll dozens of cigarettes or even to grow their own crop in gardens up to 25 square feet.
Supporters of the measure said making marijuana legal could save the state $200 million a year by reducing public safety costs and generate tax revenue for local governments.
One poll showed a slim majority of California voters support legalizing and taxing marijuana to bridge the state budget deficit.
Marijuana is illegal under federal law.