LINCOLN, Neb. (AP) — Organizers of a petition drive to legalize medical marijuana in Nebraska say they’re hitting their early signature goals with help from an all-volunteer network, but opponents are mobilizing to fight the measure if it appears on the 2020 ballot.

Volunteers have already gathered more than 15,000 signatures in their quest to place the issue before voters in the 2020 general election, and campaign organizers haven’t even started using paid signature collectors, who are generally needed to ensure a successful petition drive.

“We keep picking up momentum, and we feel like we’re hitting our goals,” said state Sen. Anna Wishart, a co-chair of Nebraskans for Sensible Marijuana Laws. “Right now, we’ve got people volunteering in many counties across the state. That’s how popular this is.”

The ballot measure would guarantee a constitutional right to buy, use and grow marijuana if a doctor recommends it, with no restrictions on which medical needs qualify. It also would allow users to smoke the drug in homes or other private settings and prevent state lawmakers from imposing an undue burden on access to the drug. If voters approve the measure, users would be allowed to grow an “adequate” supply.

Nebraska lawmakers have rejected medical marijuana bills three times, even though some of the measures would have banned marijuana smoking and imposed tight controls on how much one person can possess. Frustrated with the Legislature’s unwillingness to legalize the drug, activists have shifted their focus to the kind of ballot initiative that succeeded in Utah, Oklahoma and other conservative states. Medical marijuana is already legal in 34 states and Washington, D.C. Ten states and Washington have legalized recreational use.

Nebraskans for Sensible Marijuana Laws has received more than $6,000 in cash and in-kind contributions so far from the Marijuana Policy Project, a Washington-based group that helped lead successful campaigns in Maine, Massachusetts, Michigan, Nevada and Utah. It also reported $1,000 from the Douglas County Democratic Party, according to state campaign finance records. The campaign’s largest donation was $10,000 from the New Approach PAC, a Washington-based organization that has backed pro-marijuana petition drives in other states.

Opponents haven’t mounted an official campaign to challenge the measure, but they have formed a nonprofit group called Smart Approaches to Marijuana Nebraska to highlight the pitfalls of marijuana legalization.

Smart Approaches to Marijuana Nebraska has already started airing statewide radio ads, although the group’s nonprofit status prohibits its members from mentioning the ballot initiative or urging voters to reject it. Unlike the petition drive campaign, Smart Approaches to Marijuana Nebraska doesn’t have to disclose its donors.

The measure has also drawn opposition from Gov. Pete Ricketts and former University of Nebraska football coach and athletic director Tom Osborne.

“Nebraskans of all walks of life have heard the myths that are promoted by the marijuana industry, but when they receive factual information about how it preys on vulnerable populations, their opinions change very quickly,” said John Kuehn, a former state senator who is co-chairing the group alongside former Nebraska Gov. Kay Orr. “A little education goes a long way.”

Kuehn argued that the marijuana industry uses the term “medical marijuana” as part of a longer-term push toward legalizing the drug for recreational use.

The Nebraska campaign still has nearly a year until the July 2, 2020, deadline to present its signatures to the Nebraska secretary of state’s office.

About 122,000 valid signatures are required to qualify the measure for the ballot, and organizers are aiming to gather at least 185,000 to account for those that get rejected. Circulators also have to gather a minimum number of valid signatures from at least 38 of Nebraska’s 93 counties.

Wishart said circulators are gathering signatures at parades, concerts, county fairs, farmers’ markets and other summer events. The campaign recently hired two field directors to manage the statewide volunteers.

She said the campaign eventually plans to use paid petition circulators, but organizers right now are trying to conserve their resources for the election.

Marijuana legalization petitions have failed to reach the Nebraska ballot in the past, but most weren’t well-organized and lacked the financial support needed to gather enough signatures.

The newest campaign is also co-chaired by state Sen. Adam Morfeld, a veteran of ballot initiatives who helped lead last year’s successful petition drive to expand Medicaid in Nebraska.

“The coalition this time is broader, and the level of experience is deeper,” Morfeld said. “We have financial resources both locally and nationally. That’s not to disparage any of the past efforts. It has all led up to the support we have today.”