So far, the most outspoken groups on the issue are those affiliated with California's legal medical marijuana industry and law enforcement officials who vehemently oppose any loosening of drug laws.
But the campaign that unfolds before the November election could yield some unusual allies: free-market libertarians joining police officers frustrated by the drug war to support the measure, and pot growers worried about falling prices pairing with Democratic politicians to oppose it.
Others believe legalizing and taxing the drug could improve the state's flagging economy.
"We spend so much time, our police do, chasing around these nonviolent drug offenders, we don't have time anymore to protect our people from murders and child molesters," said Jack Cole, president of Law Enforcement Against Prohibition, a group that plans to champion the California proposal between now and the election.
The initiative, also known as the "Tax Cannabis Act," received enough signatures this week to qualify for the November ballot. If it is approved, California would become the first state to legalize marijuana for recreational use by adults. The measure would also give local governments the authority to regulate and tax pot sales.
According to campaign finance records, nearly all of the more than $1.3 million spent on the campaign to qualify the question for the ballot came from businesses controlled by the proposal's main backer, Oakland medical marijuana entrepreneur Richard Lee.
Lee operates a medical marijuana dispensary and cafe in downtown Oakland and is the founder of Oaksterdam University, which trains people to run their own medical marijuana businesses. According to the school, more than 5,000 students have completed their programs.
The largest donations from an individual not connected to the marijuana business came from George Zimmer, founder and chief executive of the men's clothing chain Men's Wearhouse.
Television viewers know Zimmer as the Fremont-based company's longtime pitchman in commercials. But he is also known as a longtime supporter of efforts to liberalize the nation's drug laws.
Opponents contend that the legalization effort will pit a few wealthy individuals against regular Californians who will provide the groundswell needed to defeat the measure.
"You have rich dilettantes who want to legalize drugs and ordinary people who consider the ramifications of legalization on their communities and their families," said John Lovell, a lobbyist representing several law enforcement groups opposed to the initiative.
Lovell pointed to the lopsided defeat of a 2008 ballot issue that would have pushed treatment instead of prison for drug offenders as a sign of voters' leanings. Supporters of the measure heavily outspent opponents, but it was defeated 59 to 41 percent.
The anti-legalization campaign has not reported any contributions yet, but workers are reviewing what they believe are major flaws with the ballot initiative. They say the proposed law would allow pot to be grown in public parks and fail to prevent people with prior drug convictions from selling pot.
Meanwhile, some well-known liberals have come out against it, including the state's presumptive Democratic nominee for governor, Attorney General Jerry Brown.
Brown, who was seen in the 1970s as an icon of California's counterculture, told the San Francisco Chronicle earlier this month that he was "not going to jump on the legalization bandwagon."
"We're going to get a vote of the people soon on that, but I'm not going to support it," he said.
Legalized marijuana in California, the nation's most populous state, would represent a sea change in the nation's drug laws and put the state in direct conflict with the federal government because pot is still illegal in the eyes of federal officials.
On Thursday, a Department of Justice spokeswoman said it was too soon to speculate on whether federal authorities would sue to keep the measure from becoming law.
The administration relaxed its prosecution guidelines for medical marijuana last year, but President Obama's drug czar has said the White House strongly opposes any efforts to legalize pot.
"Marijuana legalization, for any purpose, remains a non-starter in the Obama administration," Gil Kerlikowske, director of the Office of National Drug Control Policy, said last year. "It is not something that the president and I discuss. It isn't even on the agenda."
California in 1996 became the first of the 14 states that have legalized medicinal marijuana. Many jurisdictions around the country have also decriminalized marijuana to the point that low-level possession offenses are not prosecuted.
States such as California and Colorado have also been struggling to deal with an explosion in the number of medical marijuana dispensaries in recent years, a trend that has made pot readily available to the public.
A decision by California to legalize pot could lend momentum to the entire legalization movement, just like its historic 1996 law did for medical marijuana.
Legislators in Rhode Island are considering a plan to decriminalize pot, and a group in Nevada is pushing an initiative that marks the state's fourth attempt in a decade to legalize the drug.
Lawmakers in Washington state recently killed a plan to legalize the sale and use of marijuana, though lawmakers there did expand the pool of medical professionals who could prescribe the drug for medicinal use.
The ballot measure in California would allow people 21 years and older to possess up to one ounce of marijuana, enough for dozens of joints. Residents also could grow their own crop of the plant in gardens measuring up to 25 square feet.
The proposal would ban users from using marijuana in public or smoking it while minors are present. It also would make it illegal to possess the drug on school grounds or drive while under its influence.
Proponents of the measure say legalizing marijuana could save the state $200 million a year by reducing public safety costs. At the same time, it could generate tax revenue for local governments.
Law enforcement officials are promising a vigorous fight to ensure that marijuana never becomes legal in California. They believe legalized marijuana would increase crime and violence, deepen the nation's drug culture and lead teenagers to abuse pot.
The California Police Chiefs Association, Mothers Against Drunk Driving and groups such as the youth-oriented Drug Abuse Resistance Education also plan to oppose the idea.
Not everyone in law enforcement is opposed to the measure, however.
"We believe by voting for that initiative you can actually save lives," Cole said.