A Michigan grassroots group says it has gathered enough petition signatures to put a measure on the 2018 ballot that would allow voters to choose whether to amend the state constitution to create an independent redistricting commission.

The group, called Voters Not Politicians, plans to turn in more than 425,000 signatures to the Michigan Secretary of State’s Office on Monday to begin the verification process. The group needs at least 315,654 valid signatures to get the measure on the ballot. The campaign and petition collection effort was run completely by volunteers, though the group has recently brought on paid public relations, fundraising and legal assistance.

An independent redistricting commission could have significant consequences in Michigan, which the Brennan Center for Justice describes as one of the most severely gerrymandered states in the country. Following the 2010 census, Michigan Republicans controlled the redistricting process and drew the lines in such a way that gave Republicans an advantage of two to three additional seats in Congress, according to the Brennan Center’s analysis.

The ballot initiative aims to make the redistricting process more fair by amending the Michigan Constitution to create a 13-member redistricting commission with four Democrats, four Republicans and five independents. The commission would be required to hold at least 10 public hearings as part of the redistricting process.

Katie Fahey, the president and treasurer of Voters Not Politicians, said the effort to gather hundreds of thousands of signatures started with a single Facebook post days after the 2016 election. At the time, she was hearing from both Democrats and Republicans who didn’t trust politicians.

“When I was thinking about that, I remembered in school learning about redistricting and about gerrymandering and how that’s one of our really fundamental systems that democracy has, yet in many states it is corrupt that we have politicians choosing their voters, instead of voters choosing their politicians,” she told HuffPost. “It just felt like a really good time to find an issue we could talk about no matter what your political belief was and actually start restoring some of that faith in democracy and those systems.”

Fahey, who works in the waste and recycling industry to help set up recycling programs, has never worked on a political campaign. She initially thought only her friends and family would respond to her Facebook post about gerrymandering. Instead, she got a swell of support from strangers and formed a board of directors with nine people whom she wouldn’t meet in person for three months. Today, she says, 10,000 people have helped the campaign. Fahey and her group will be two months ahead of the deadline to turn in signatures when they do so on Monday.

It’s an effort that has impressed even Bob LaBrant, a GOP lawyer who has led efforts to stop ballot measures in the state in the past.

“They’re making the petition management industry look bad. They’ve done for seemingly free what outfits charge a substantial amount of money to do,” LaBrant told The Associated Press. “Their grassroots effort has been remarkable.”

LaBrant appears to be preparing a legal challenge to the possible ballot measure. He told Bridge Michigan the ballot initiative was proposing a “general revision” to the state constitution, which would require a constitutional convention.

The U.S. Supreme Court is considering two cases that could reshape the way redistricting is done following the 2020 census. The high court could use the cases to articulate a standard for the first time of when redistricting goes so far to benefit a political party that it is unconstitutional.

During a panel on gerrymandering at a conference hosted by the American Legislative Exchange Council earlier this month, Guy Harrison, a Republican operative who has focused on congressional races, told a room full of state lawmakers that any state with a nonpartisan commission had to have some way of ensuring the people who got picked to serve on the commission were actually nonpartisan. He also accused Democrats of using legal challenges to partisan gerrymandering as a way to try to pick up elected seats they could not win politically.

Under the Michigan proposal, anyone in the general public would be able to apply for a seat on the commission and the Secretary of State’s Office would randomly send out 10,000 mailers inviting people to apply. Applications would be statistically weighted and then chosen at random. Those applying cannot have served as a lobbyist, candidate or officeholder for six years or be closely related to anyone who has. They will be barred from serving in a partisan elected office for five years after they finish their time on the commission. LaBrant told the AP that the proposal would result in “neophytes” being responsible for the state’s redistricting process.

Michigan Republicans have highlighted a majority of people on the Voters Not Politicians board have given to Democrats, but Fahey said the effort wouldn’t give one party an advantage and said it was really focused at making things more fair.

“We have had both political parties gerrymander our system. Even in our upcoming election, we don’t know who will be in charge of this process. It could go either way,” Fahey said. “If you just read our policy, it directly says one political party cannot take advantage of the other when drawing these maps. It has to actually be fair and representative of how the people of Michigan vote.”