LINCOLN, Neb. — Backers of an effort to legalize medical marijuana in Nebraska have filed formal paperwork for a statewide ballot campaign.

Nebraskans for Sensible Marijuana Laws submitted their proposed constitutional amendment Tuesday to the Nebraska Secretary of State’s office.

State Sens. Anna Wishart and Adam Morfeld, of Lincoln, are co-chairing the effort to place the issue on the 2020 ballot.

Wishart has introduced a bill that would allow lawmakers to legalize the drug for medicinal purposes, but it faces stiff opposition from state and local law enforcement, Gov. Pete Ricketts and prominent Nebraskans including former Husker football coach Tom Osborne.

Legalization supporters have said they will pursue the ballot campaign if lawmakers don’t pass a measure this year.