The state Democratic Party decided Sunday not to endorse the marijuana legalization initiative on the November ballot after a swift, passionate debate that left little doubt most Democrats in the hotel meeting room intend to vote yes at the polls.

The party decided to adopt a neutral position on Proposition 19, leaving the many local Democratic committees and organizations free to endorse the measure.

Advocates for an endorsement cited many reasons to back the initiative, but opponents pressed one overriding concern: a yes vote could damage statewide candidates in competitive races.

“We’re concerned that our candidates, Jerry Brown, Barbara Boxer and others, who have actually come out against this are going to be compromised,” said Steve Preminger, the chairman of the Santa Clara County Democratic Central Committee, “so we’re going to get lost in a discussion about the merits of whether we should legalize or not, when, really, we the Democratic Party want to put all of our efforts into electing our ticket.”

Robert Cruickshank, public policy director for the Courage Campaign, which backs progressive causes, called for the vote in an attempt to overturn a party committee’s recommendation to adopt a neutral position. He started by reminding the assembled Democrats that the party’s chairman, former San Francisco state Sen. John Burton, has said pot was the issue that would motivate young voters to go to the polls in this off-year election.

“If we endorse Proposition 19 and take a courageous position to support reform, just as we took courageous positions on same-sex marriage and other contentious issues, we will win the moral argument, we will win Proposition 19 and we will win races in November,” Cruickshank said.

Proposition 19 would allow Californians 21 and older to grow, possess and transport marijuana, and allow cities and counties to opt to regulate and tax marijuana sales.

Burton said he believes the issue will engage young voters, a key constituency for Democrats. He abstained on the vote but said he was not convinced that an endorsement would hurt Brown’s campaign for governor, Boxer’s bid for reelection to the U.S. Senate or the other Democrats running for top state offices. “The statewide candidates, I guess, are all antsy,” he said.

He said he would vote for the initiative, adding: “And I haven’t had a joint in 30 years.”

The party’s executive board, which includes elected officials and party representatives from across the state, voted 101 to 85 against an endorsement. But the Democrats, despite taking a cautious stance, appeared solidly behind the initiative, cheering and whooping much more raucously for the pro-endorsement speakers.

Dan Rush, an official with Local 5 of the United Food and Commercial Workers, who is running the legalization campaign’s labor outreach, said an endorsement would have been a “great boost” but that a neutral position was still a victory. “We could have gotten a resounding no,” he said.

john.hoeffel@latimes.com