For the second time in two years, Missouri is upending the way it maps out the districts used to elect lawmakers to seats in the House and Senate in Jefferson City.

Unofficial results showed Amendment 3 passing 51 percent to 49 percent, meaning bipartisan commissions will again take center stage in the mapmaking process and notions of drawing districts to produce more competitive elections will fade to the background.

Amendment 3's slim margin of victory was very different from the verdict the last time Show-Me State voters had their say on the once-in-a-decade redistricting process.

In 2018, roughly 62 percent cast their ballots for the so-called "Clean Missouri" initiative, which put a "nonpartisan state demographer" in charge of drawing the districts and required map drawers to prioritize producing more competitive elections and an assembly that better reflects statewide votes.

But on Tuesday, Republican lawmakers' proposal to gut that plan ran up the score in rural Missouri to eke out a reversal.

Metro areas kept Clean Missouri in the game.

Kansas City and St. Louis came out strong against the idea, and more than 51 percent of Greene County voted no along with them, but it wasn't enough.

Clean Missouri backers conceded defeat shortly after midnight Wednesday.

"Thousands of volunteers from across the state and across the political spectrum have been working for years to pass and then defend fair redistricting rules in our constitution, and today we came up short," the campaign said in a statement.

The Missouri Farm Bureau, which backed the initiative, delighted in the news hours later, pointing out that the "no" campaign outspent them by millions of dollars.

"Thank you, Missouri, for standing up against out-of-state dark money trying to lie to us and push their partisan agenda," the organization tweeted.

The return to the 2018 rules marks a big victory for Republican lawmakers who worked for two years to get redistricting back in front of voters.

Prior to 2018, districts were to be drawn by bipartisan commissions appointed by the governor.

The rules tried to address concerns about gerrymandering by requiring statehouse districts to be "compact" and "contiguous."

Appellate judges were also held in reserve to take over if the bipartisan commissions deadlocked.

But under those rules, Republicans still managed to take 71 percent of the 163 House seats in 2018 while winning an average of just 57 percent of the two-party vote in each contest.

After Clean Missouri passed, Republicans took some heat for trying to turn back the clock, with Democrats accusing them of "overturning the will of voters."

Figures like Senate Majority Leader Caleb Rowden, R-Columbia, said voters didn’t really understand what they were doing, while others suggested Clean Missouri purposefully bamboozled the public by rolling the changes together with lobbyist gift limits and campaign finance restrictions (a tactic also used by Amendment 3).

They also said their amendment would prevent maps with “spaghetti” string districts combining urban, suburban and rural areas drawn to make races more competitive, though opponents disputed that.

It may actually more funny business possible with a change to how map drawers calculate the population of each district, though.

Rather than using  “total population,” which requires counting immigrants, children and nonvoters, Amendment 3 uses a broader “one person, one vote” that could be used to draw districts based on eligible voters, or adult citizens.

If that change takes place, researchers who supported Clean Missouri say it could strengthen the influence of old, white and rural Missourians — who generally vote Republican — at the expense of minority communities and young people — who generally vote Democratic.

But the fight over that likely isn't over yet.

Clean Missouri backers vowed Wednesday to stay engaged with the redistricting process as it moves forward after this year's census, and they'll likely have plenty of resources to do so from Missourians and deep-pocketed out-of-state contributors.

"We are committed to ensuring as fair an outcome as possible when new maps are drawn in 2021," the campaign's statement said. "Amendment 3 was written to allow for truly radical gerrymandering, but it does not require it."

Elad Gross, a former assistant attorney general who ran unsuccessfully for the big job this year, went one further and tweeted a threat to sue if Amendment 3 is used "to take away our voice in government."

That may not be just talk.

Sen. Dan Hegeman, R-Cosby, who sponsored Amendment 3 in the legislature, told a recent forum the plan would simply codify a recent Supreme Court decision, Evenwel v. Abbott, on how districts should be apportioned based on the principle of "one person, one vote."

But that decision just said that counting everyone living in a district is an OK way to interpret the principle of “one person, one vote,” nothing more.

And in that 2016 decision, two conservative justices suggested they would consider alternatives to counting everyone if and when they came up.

In a concurring opinion, Justice Clarence Thomas wrote that in his view, states have "wide latitude" on the issue..

They "can use total population, eligible voters, or any other nondiscriminatory voter base," he wrote.

And when Hegeman was debating the issue in the Senate earlier this year, he suggested Missouri might well go in a new direction.

"We’re looking at the people that vote," he said. "The people that are able to vote are the people that are counted. Not registered voters, but the opportunity to do that."