The campaign to put an initiative partially legalizing marijuana on the 2012 Colorado ballot says it already has collected 35,000 signatures, but it has been dogged in the effort’s earliest stages by a persistent foe: other marijuana-legalization supporters.

At volunteer meetings and signature-gathering drives, a splinter group of pro-legalization activists has shown up to argue that the measure doesn’t go far enough. At one such event, an activist allegedly took a clipboard of signed petitions and tossed it into the trash. At another, an activist was arrested for trespassing after refusing to leave.

“It’s disingenuous,” Corey Donahue, the activist who was arrested during a meeting last month at the Boulder Public Library, said of the initiative. “I think they’re lying to the people of Colorado.”

Mason Tvert, one of the leaders of the initiative campaign, admitted the activists have been a slight headache. But he said they ultimately represent just a tiny, if noisy, segment of the population.

“This is a coalition of tens of thousands of supporters,” Tvert said of the initiative’s backers. “We’re not hearing concerns expressed by any more than that one particular group.”

The proposed initiative, which is currently named the Campaign to Regulate Marijuana Like Alcohol, would allow anyone 21 and older legally to possess up to an ounce of marijuana and grow six cannabis plants. People also would be able to purchase marijuana from pot shops, which the state would license and regulate in much the same way it does medical-marijuana dispensaries. Some marijuana-related offenses, such as sales to minors or driving under the influence, would remain illegal.

Already, four issue committees have formed to support the effort, according to state records. One, called the Coalition to End Marijuana Prohibition, is largely funded with a $10,000 donation from the Marijuana Policy Project, a national marijuana-legalization organization. Three other groups have not yet had to report their finances.

The campaign must collect signatures from 86,000 valid Colorado voters by Jan. 6 to get on the 2012 ballot. If it does that, it would then have an unusually long time to win over voters ahead of the election.

“We’re trying to get this measure on the ballot as soon as possible so we can get to focusing on educating voters and building a winning campaign,” Tvert said.

The problems Donahue and other activists have with the proposed initiative start with the campaign’s name, which Donahue says misleads voters because the regulations around marijuana would be much more strict than those around alcohol.

“It’s going to have regulations, so it’s going to create more rules,” Donahue said. “Regulation isn’t legalization.”

Amid such complaints, marijuana activist Michelle LaMay has filed a new proposed initiative, which would prohibit state and local courts in Colorado from punishing people for marijuana-possession crimes.

If this debate sounds familiar, that’s because it largely parallels debates around medical-marijuana regulation, where buttoned-down dispensary owners arguing for legitimizing regulations clash with outspoken activists who want more personal freedoms. It also mirrors a portion of the debate around California’s Proposition 19, a failed 2010 effort to legalize marijuana in that state that divided marijuana supporters there.

“People who support ending marijuana prohibition don’t necessarily agree what to replace prohibition with,” said Stephen Gutwillig, the California director for the Drug Policy Alliance, which supports Tvert’s initiative.

But Gutwillig said marijuana-reform infighting likely didn’t play a role in Proposition 19’s downfall.

“There wasn’t evidence they didn’t vote for Prop. 19 because it was too conservative,” Gutwillig said.

John Ingold: 303-954-1068 or jingold@denverpost.com