It seemed an easy sell in California: The state that gave us medical marijuana would allow pot for recreation.

Then came the ads, newspaper editorials and politicians, warning of a world where stoned drivers would crash school buses, nurses would show up at work high and employers would be helpless to fire drug-addled workers.

A day after voters rejected Proposition 19, marijuana advocates wondered how they failed in trendsetting, liberal California.

Was it the fear of the unknown? An older electorate more likely to oppose pot? Voters reluctant to go any further than they already had with the nation’s most lax pot laws? Fear of crossing swords with a federal government still intent on enforcing its ban on the drug?

Whatever the reason, activists vowed Wednesday to push on in California, as well as in states that rejected other pot measures Tuesday.

“Social change doesn’t happen overnight,” said Paul Armentano, deputy director of the National Organization for Repeal of Marijuana Laws.

In South Dakota, voters rejected for the second time a medical marijuana measure — a step first taken by California in 1996 and by 13 other states since. Oregon voters refused to expand their medicalmarijuana program to create a network of state-licensed nonprofit dispensaries.

A medical marijuana measure on Arizona’s ballot remained too close to call Wednesday.

California’s initiative, which would have allowed adults age 21 and older to possess and grow small amounts of marijuana, failed 54 to 46 percent. An Associated Press analysis of exit and pre-election polls found voters opposed Prop 19 regardless of race, gender, income or education level.

Blacks and Latinos, for example, opposed the measure at about the same rate as whites. That despite evidence that pot advocates presented during the campaign that minorities are disproportionately arrested on marijuana offenses.

“There is a sense of people wanting to move into a new policy … but still being wary of what that change might mean,” said Ethan Nadelmann, director of the pro-legalization Drug Policy Project.

Roger Salazar, a spokesman for the successful campaign to defeat Prop 19, agreed that misgivings about possible social problems from increased marijuana use helped seal the measure’s fate.

But he also blamed backers for leaving it up to local governments instead of the state to set sales regulations. He also faulted them for promoting the measure as a revenue windfall for the state and a way to undercut drug traffickers and free up police to pursue more serious crimes.

“The risks of legalizing something as important as marijuana were far greater than the potential benefits, and the benefits were far from guaranteed,” Salazar said. “If they are going to come back with something, it has to be a lot more tightly written.”

Preliminary election returns showed Prop 19 winning in 11 of 58 counties, with the strongest support in San Francisco and Santa Cruz.

But in a sign of what a tough sell it was, the measure lost in the state’s vaunted marijuana-growing region known as the “Emerald Triangle” of Humboldt, Mendocino and Trinity counties. Many in the region feared the system they created would be taken over by corporations or would undercut a cornerstone of the local economies by sending pot prices plunging.

Those most anxious about the economy were not convinced that legalizing pot was worth the potential tax revenue or jobs created by a newly legal marijuana industry.

A Los Angeles dispensary manager said the proposition was a step in the right direction, though its failure wasn’t necessarily bad.

“The fact it didn’t pass is not really so bad for us because it keeps the status quo for dispensaries and collectives that are already operating,” said Tim Blakeley, 44, who manages Sunset Junction Organic Medicine.

“People need more time to get used to the idea of legalized pot,” he said.

For many in California, the status quo was also fine but for another reason,

Just a month before the election, Gov. Arnold Schwarzenegger signed legislation that made possession of up to an ounce of marijuana the equivalent of a traffic ticket, subject to no more than a $100 fine and no arrest or criminal record.

Prop 19 supporters said they believed Schwarzenegger signed the bill to undercut any sense of urgency around marijuana legalization.

Abbey Kaufman and Matt McDonald toked up “a few blunts” during the Giants World Series celebration in front of San Francisco City Hall despite a strong police presence.

The 20-year-old San Franciscans said they each voted yes but both said they weren’t disappointed Prop 19 failed.

“Right now, you can smoke as much pot as you want on the streets of San Francisco,” Kaufman said. “If it had passed, marijuana would have been treated like booze and there would be a big crackdown on public smoking.”

“I think a lot of stoners voted yes just because, but I think we’re better off that it didn’t pass.”

Richard Lee, the Oakland, Calif., medical marijuana entrepreneur who sponsored Prop 19 and spent $1.4 million of his own money to qualify the measure for the ballot and try to get it passed, drew hope in the generational divide among the voters.

The only unequivocal support for the measure came from voters under 30, though even they were not as united in their support as voters 65 and older were in their opposition.

Lee said the fact that 3.4 million Californians cast ballots for legalizing marijuana and that Prop 19 came within 9 percentage points of passing were victories themselves

He noted that since younger voters supported the initiative, a generation that does not fear the drug would one day constitute a majority of the population.

“The issue is generational,” he said. “Many of the biggest contributors to the campaign were younger and based in Silicon Valley, representing a changing of the guard of political influence and leadership.”

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Associated Press writers Paul Elias in San Francisco and Shaya Tayefe Mohajer in Los Angeles contributed to this report.