A sleeper issue has emerged among DFL candidates in the 2018 governor’s race: Marijuana.

St. Paul Mayor Chris Coleman, state Reps. Erin Murphy, Tina Liebling and Paul Thissen, and U.S. Rep. Tim Walz all support legalizing marijuana for recreational and not just medical use. Among the major DFL candidates, only State Auditor Rebecca Otto declined to do so.

“When you confront the reality of the cost of criminalization vs. the benefits of legalization, I think the benefits outweigh the costs,” said Coleman, whose campaign approached the Star Tribune to discuss the issue.

The candidates’ sudden embrace of marijuana legalization underscores how quickly the issue is moving and illustrates the rapid changes underway in the DFL Party.

In a 2014 Star Tribune Minnesota Poll, just 30 percent of respondents said the state should legalize marijuana for recreational purposes, while 63 percent opposed.

Since then, however, legalization has spread from Colorado and Washington state, which were early adopters, to California, Massachusetts and four other states plus the District of Columbia. A wave of largely positive publicity has followed, with tales of tax revenue for schools, tourism dollars and a decline in marijuana-related arrests and the costs of prosecuting them.

In a 2016 Gallup poll, 60 percent of Americans said they favor legalization, the highest support in the poll’s half century of asking about the issue.

The Minnesota DFL is increasingly younger, more diverse and more urban — groups that favor legalization by big margins. The DFL candidates for governor are trying to capture those demographics as they chase the delegates needed to win the endorsement and the party’s nomination next year.

The four major Republican candidates for governor are all opposed to marijuana legalization.

“My focus will be on fixing those things that are making life difficult for Minnesota’s middle class. Not legalizing pot,” said Hennepin County Commissioner Jeff Johnson, who was the GOP’s 2014 nominee and is running again.

Like Coleman, other DFL candidates cited prohibition’s disproportionate effects on people of color.

“The system we have had was that we looked the other way, unless you’re a person of color, in which case you face the threat of arrest and incarceration,” said Walz, who has also been active trying to get medicinal marijuana to military veterans as part of his work in Washington.

Blacks in Minnesota were 6.4 times more likely than whites to be arrested for marijuana possession in recent years, according to a report by University of Minnesota geographer Nicole Simms.

But opposition among Republicans and even among some DFLers demonstrates that growing public support for marijuana legalization may not translate into swift action at the State Capitol.

DFL Gov. Mark Dayton, whose term ends in 2018 and is not running for re-election, is opposed to marijuana legalization. Republicans will continue to control the state Senate at least through the 2020 election, and Minnesota lacks the kind of voter initiative process that accommodated marijuana legalization in the first wave of states.

Another Republican gubernatorial candidate, state Sen. David Osmek, of Mound, said he opposes legalization because he has “close friends who have had kids get caught up in pot, who proceeded to go from pot to stronger drugs, and they’re both incarcerated.”

“I see it as a problem for us as a society and we shouldn’t go that direction,” Osmek said.

Coleman rejected Osmek’s argument: “Alcohol is the biggest gateway drug out there.”

Both Osmek and Keith Downey, the former Republican Party chair, now running for governor, said they favor medical cannabis. The other major candidate, state Rep. Matt Dean, voted against legalizing marijuana in 2014, when the Legislature created Minnesota’s current program.

Thissen, now among the DFL candidates, was state House speaker at that time. He recently wrote a lengthy defense of legalizing marijuana on the website Medium.

The 2014 law created a tight regulatory regime that sought to prevent an unwitting, chaotic slide from medical into recreational quasi-legalization. But the law has been called overly restrictive by patients and some doctors.

Otto was asked about legalization at a forum this summer and declined to support it: “I want to fund the schools in an honest way in our state. I feel like we have to say these are our values, and I don’t to have to sell marijuana to fund our schools,” she said.

Coleman said Minnesota should prepare for the inevitable and be ready to capture the benefits of legalization like tax revenue and new jobs, while mitigating the costs, including addiction and traffic safety.

“To me it’s not a question of if, it’s a question of when, and I think the time is now,” Coleman said.