JEFFERSON CITY, Mo. (AP) — Two years after Missouri voters enacted a first-of-its-kind initiative intended to create “partisan fairness” in voting districts, they have changed their minds.

Before the measure could be used, voters reversed key parts of it in Tuesday’s election. They opted instead to return to a method that will let commissions composed of Democratic and Republican loyalists redraw state legislative districts after census results are released.

The Missouri vote broke a string of nationwide electoral victories for redistricting reform advocates and opened the potential for Missouri to experiment with another nationally unique model — one that could exclude noncitizens from the population totals used in redistricting.

Some supporters of the 2018 initiative, known as Clean Missouri, asserted that voters were tricked into undercutting it by the Republican-led Legislature, which placed Amendment 3 on this year's ballot. The amendment passed with just 51% of the vote.

“I’m not sure that voters fully understood that they were in fact repealing what they had passed in 2018 rather than building on it,” said Yurij Rudensky, a redistricting attorney at the Brennan Center for Justice at New York University School of Law.

By contrast, some Republican lawmakers contend that voters were misled by the original measure.

“I don’t think there’s a problem with letting voters reconsider it,” said Republican state Sen. Dan Hegeman, who sponsored this year's measure. He said it returns redistricting to “a tried and true method."

Missouri's 2018 initiative had been part of a national movement aimed at combating partisan gerrymandering, which occurs when politicians draw voting districts to give themselves or their political parties an advantage in future elections.

Voters in Colorado, Michigan, Ohio and Utah all passed redistricting overhauls that year. Virginia voters approved a constitutional amendment Tuesday that will shift redistricting power away from its legislature, currently controlled by Democrats, to a bipartisan commission of lawmakers and citizens.

The original Clean Missouri measure also limited lobbyist gifts and campaign contributions to lawmakers, and made lawmakers' records open to the public. The ballot summary listed all of those things while also noting it changed the “process and criteria for redrawing state legislative districts.” But the ballot summary provided no specifics of how redistricting would change.

The 2018 measure directed a new nonpartisan demographer to draw state House and Senate districts to achieve “partisan fairness” and "competitiveness" based on the average votes that Republicans and Democrats received in the three previous elections for president, U.S. Senate and governor. It made Missouri the first state to use a specific formula, known as the “efficiency gap," to calculate political fairness.

An Associated Press analysis determined that the formula likely would have allowed Democrats to cut into Republicans' supermajorities in the Missouri Legislature in the upcoming 2022 elections.

While seeking to overturn it, Republican lawmakers argued the Clean Missouri measure actually would result in more gerrymandering by forcing urban Democrats and rural Republicans to be combined into elongated districts to try to achieve competitive elections.

This year's Republican-backed ballot measure eliminated the nonpartisan demographer, placed redistricting back in the hands of bipartisan commissions, elevated the importance of compact districts and dropped “partisan fairness” and “competitiveness” to the bottom of the priority list.

Although technically keeping the formula to calculate fairness, the new measure allows a variance so large that maps considered to be extreme gerrymanders by the formula's creators would still be OK.

“It has been diluted almost to the point of irrelevance,” Rudensky said.

Republican lawmakers also paired the redistricting changes with slightly lower limits on lobbyist gifts and campaign contributions. Hegeman said they merely were mirroring the approach of the original Clean Measure measure.

“Our biggest hurdle in the whole thing was ballot language that voters could look at and think, `Oh, there must be some actual reform going on,” said Sean Nicholson, a Democratic consultant who led the Clean Missouri campaign and the opposition to the Republican measure. "We worked hard in the whole campaign to try and let voters know that someone was trying to dupe them. We obviously came up short on that.”

The Republican-backed measure also deleted a requirement to base districts on the total population tallied by the census. It instead references a Supreme Court standard of “one person, one vote.” Hegeman said the measure's silence on “total population” could give redistricting commissioners the option of using only the citizen population.

Opponents argued it also could let commissioners use only the voting-age population, which could exclude children from the count.

All states currently base redistricting on total permanent population. An attempt to exclude noncitizens from Missouri's redistricting likely would be challenged in court but may have little political effect, because Missouri has relatively few non-citizens, said Nick Stephanopoulos, a law professor at Harvard University.

“It’s almost inviting unnecessary controversy,” he said, and “it opens the door to lots of legal jeopardy.”