SAN FRANCISCO » Proposition 19, which would have legalized marijuana in California, received more votes than the Republican nominee for governor, Meg Whitman.

It also received untold news coverage, bringing the debate a new level of legitimacy in the eyes of many supporters. And while it lost — with 46 percent of the vote — its showing was strong enough that those supporters are confidently planning to bring it back before voters in California, and perhaps other states, in 2012.

"We’re going to win," said Aaron Houston, the executive director of Students for Sensible Drug Policy, a nonprofit group in Washington. "And we’re going to win a whole lot sooner than anybody thinks."

But for all that heady talk, proponents of legalization still face a series of stiff challenges, including winning over older members of the electorate — who overwhelmingly rejected the measure — as well as wary elected officials from both political parties. And while most advocates say that Proposition 19 was a high-water mark for the movement, many acknowledge that the road to legalization will also require new campaign ideas, more money and a tighter, more detailed message to overcome persistent cultural concerns about the drug.

"The Prop. 19 campaign really did not do anything to help people get over their fear of marijuana, the substance," said Steve Fox, director of government relations for the Marijuana Policy Project, a national organization that has helped pass medical marijuana laws. "If people believed marijuana is a dangerous drug that people shouldn’t use before the campaign, that is probably how they felt at the end of the campaign."

In California, Proposition 19’s showing was exactly in line with a pre-election Gallup survey that found 46 percent of Americans’ favoring legalization. That support has been growing for years, particularly in the Western states, where 58 percent now support legalization, according to Gallup.

But in an off-year election, one critical demographic for the "Yes" side simply did not show up in California: the youth vote.

"It appears that the bump that we hoped for, those hopes were overstated," said Ethan Nadelmann, the executive director of the Drug Policy Alliance, which advocates for liberalizing drug laws. "Clearly, we were overly optimistic."

Nadelmann said long-term trends were in the legalization movement’s favor, as were public perceptions of who marijuana users are. Now, he said, the drug is associated with "medical users, middle-class parents, nonrebellious youth."

But while Nadelmann said the presidential campaign in 2012 would undoubtedly draw more young voters, he also cautioned that trends can be fickle.

"Let’s not forget something: in 1979, people thought that marijuana was on its way to being legal," said Nadelmann, referring to state and federal efforts to decriminalize the drug during the Carter administration. "And you know what? It got flipped down. Support dropped."

Nadelmann was just one of several leaders who met last weekend for a so-called mile-high summit meeting, a combination pep rally and post-mortem in Denver. And while much of the talk was optimistic — particularly about Colorado, which will most likely vote on legalizing marijuana in 2012 — there were also some hard facts to confront, including that Proposition 19 lost even though supporters heavily outspent opponents.

Nadelmann said that spending by supporters — about $4 million — was tiny by California standards. But he said major donors would need to see more progress before committing to any future race.

"Don’t expect big money unless the numbers are there in the polling," he said.

There is also the issue of support, both political and among two demographic groups important in any statewide campaign here. No top-of-the-ticket candidate from either party in California supported Proposition 19, and the measure did not do well in Los Angeles — just 47 percent voted "yes" — or with Latino voters, particularly older ones, who voted against the proposition in large numbers, according to exit polls.

The measure also failed in many counties where marijuana is legally grown — medical use of the drug has been legal in the state since 1996 — leading to a suspicion that some growers opposed legalization because they feared it would lead to a drop in price and in profits.

There seemed to be something of a consensus that Proposition 19 — which would have legalized possession up to an ounce but left many regulatory details to localities — may not have been drafted tightly enough to win. The "No" campaign had consistently slammed the measure as a "jumbled, legal nightmare" and questioned estimates of the potential tax revenue that legalization would have brought in.

Roger Salazar, a spokesman and strategist for the campaign against the proposition, said the results showed that "details were important to the voters."

"I think the proponents of the measure overplayed their hand on taxation and control," Salazar said in an e-mail. "The measure itself did not include these components, and as soon as voters figured that out, they turned against it."

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