SIOUX FALLS, S.D. — A proposed ballot measure that would force nonprofit advocacy organizations to reveal top donors if the groups make significant contributions to ballot question campaigns would help inform voters about who is behind initiative messaging, the South Dakota House speaker said Wednesday.

The initiative comes after an election cycle dominated by ballot measure spending from “faceless” groups outside of South Dakota, Republican state Rep. Mark Mickelson said. His proposal mirrors legislation that failed this year under intense lobbying from interest groups, potentially shifting the conflict over the plan from the state Capitol to the 2018 political campaign.

“The special interests were successful in killing these ideas in a Senate committee, and I expect that they would have the same amount of success again,” Mickelson said, adding that he thinks the measure can be “marketed in a way where voters are going to support it.”

The plan would require the disclosure of the 50 largest contributors to nonprofit advocacy groups — including labor organizations, business leagues and social welfare organizations — that give $25,000 or more in a year to a South Dakota ballot measure committee.

Current state law requires that ballot question committees publicly release the names of their donors. But, nonprofit advocacy groups that contribute to those committees are able to shield their contributors under South Dakota’s campaign finance regulations.

The 2016 election season featured 10 ballot questions that attracted millions of dollars from out-of-state groups, including dark money organizations, pouring into South Dakota initiative campaigns. The precursor bill passed through the state House, but a Senate committee killed it.

The plan also aims to impose the disclosure requirement on groups that spend $25,000 or more on independent expenditures within a year. Under the proposal, if a top-50 contributor is an advocacy group, that organization would have to share its 50 largest donors.

Under the measure, groups would face fines if they didn’t comply, and they could be barred from contributing to ballot question campaigns or making independent expenditures for five years. The bill’s disclosure provisions wouldn’t apply to 501(c)(3) charities, for-profit businesses and contributors who give less than $5,000. The measure’s specific language could be changed on its path toward the ballot.

Critics have argued that South Dakota residents have the right to support causes they believe in without fear of harassment. The state’s chapter of Americans for Prosperity, the conservative advocacy group backed by billionaire brothers David and Charles Koch, helped defeat the bill during the 2017 legislative session. State Director Ben Lee said the group would likely oppose the proposed initiative.

“I absolutely think this would stifle free speech in South Dakota,” Lee said. “This was an idea that the Legislature rejected this last session, and we hope that the folks of South Dakota would reject it as well if it finds its way to the ballot.”

Supporters would have to submit nearly 14,000 valid signatures to the secretary of state by November 2017 to put it before voters in 2018. Mickelson has also proposed measures that would ban out-of-state contributions to initiative groups and raise tobacco taxes to make state technical institutes more affordable on top of the donor disclosure plan.

“It’s going to be third in my list of priorities on ballot measures, but I think we’re going to get all three of them through,” Mickelson said.