Activists who hope to make Denver the first U.S. city to decriminalize psychedelic mushrooms moved a step closer to that goal Monday by turning in ballot petitions.

The initiative, if approved by voters in the May municipal election, would apply to the use and possession of psilocybin mushrooms, also called magic mushrooms, by adults 21 and older — by making it the lowest law-enforcement priority and barring the use of city resources to impose penalties.

Though psilocybin mushrooms are classified as an illegal drug federally, the strategy echoes earlier moves in Denver to decriminalize marijuana prior to state voters’ approval of legalization in 2012.

Organizers under the name Decriminalize Denver say they have collected more than 8,000 ballot petition signatures. The first hurdle is making the ballot, which requires 4,726 verified signatures from registered voters. Given past initiatives’ rate of rejected signatures, though, the psilocybin initiative may be cutting it close.

The Denver Elections Division now has 25 days to verify each signature.

Supporters of decriminalizing psychedelic mushrooms point to studies of their safety and say they can reduce stress and opioid use, among other arguments. But other bids to decriminalize mushrooms have fallen short. In Oregon, activists plan to seek a 2020 statewide ballot measure that would allow the use of mushrooms for people with medical needs.