A Republican-backed lawsuit aimed at killing Michigan’s new redistricting commission could threaten the future of California’s landmark citizens’ reapportionment panel.

The Michigan suit, filed in federal court, charges that the rule barring politicians, partisan staffers, lobbyists, party leaders and their families from the commission is unconstitutional and should invalidate the redistricting system approved by the state’s voters in a 2018 initiative.

“In excluding certain categories of citizens from eligibility based on their exercise of core First Amendment rights, including freedom of speech, right of association and the right to petition the government, the State has unconstitutionally” blocked individuals from serving on a government body, the suit states.

California bars those same groups of people from serving on this state’s redistricting commission. If opponents of the Michigan law win their federal court case, California’s plan, which was used a decade ago and is set to go again next year, could also be in danger, said Michael Li, senior redistricting counsel for the Brennan Center for Justice at New York University.

“If the suit is successful — and that’s a big if — it could mean trouble for California’s commission,” he said. “But it would be a radical change.”

The shadow of the lawsuit isn’t slowing California’s work on preparing to put together its own commission for the upcoming redistricting. There have already been more than 11,000 applications for the 14 spots on the commission, and state officials are looking for more.

“As far as our work goes, the (state) Constitution requires us to comply with the law unless an appellate court declares it unconstitutional and therefore, we intend to carry forward the work the voters assigned to us,” said Margarita Fernández, a spokeswoman for the state auditor’s office, which is handling the applications. “We’ve had full support of members from both parties.

The similarities between the Michigan and California rules are no accident. Both initiatives were designed to block gerrymandering by taking the every-10-years post-census effort to redraw each state’s political lines away from elected officials and put it into the hands of a multipartisan citizens’ commission.

“When we did the work and research on the suit, we found a lot of what the Michigan law is based on came from California,” said Tony Daunt, the lead plaintiff in the suit. “But we filed the suit based on Michigan and the constitutional violations to our residents.”

Daunt is executive director of the conservative Michigan Freedom Fund, which is designed “to catalyze a grassroots movement in favor of our Constitutional rights.” He’s also a registered lobbyist, serves on the board of the state Republican Party, is a county party official and also served on Michigan’s equivalent of the GOP county central committee, “which disqualifies me in four different ways,” he said.

The rules in both California and Michigan call for the commission to have set numbers of Republicans, Democrats and independents. But they also list a wide range of politically active residents who aren’t eligible for the commissions.

“The most egregious part is this rule also bars parents, children,” Daunt said. “These are people who may not have been involved in politics in any manner, except voting.”

While Daunt is confident the courts will side with the suit, Li, the attorney at the Brennan Center, says the effort is little more than a Hail Mary pass to block the redistricting commission.

“The idea that you can’t have any restrictions (on who can serve on the commissions) is pretty far-fetched,” he said. “The question is whether there are reasonable expectations for those restrictions.”

The First Amendment doesn’t block every restriction, Li noted. A presidential candidate has to be at least 35 years old and a natural-born citizen who has lived in the country for 14 years. And while partisan campaigning is expected, it can’t be done within 100 feet of a polling place.

“These commissions need to be independent, but how can they really be independent if someone related to a politician is on the panel?” Li asked.

There’s nothing nonpartisan about the team behind the Michigan lawsuit. Besides Daunt, the named plaintiffs include a Republican state senator, a GOP candidate for county commissioner, a Republican national committeewoman and the president of the Republican Women’s Federation of Michigan.

The suit is getting financial backing from Fair Lines America, a nonprofit with links to the National Republican Redistricting Trust.

Former Wisconsin Gov. Scott Walker, finance chairman for the GOP group, was quick to praise the Michigan suit.

“No American should be barred from holding a government position because they, or someone they are related to, exercised their Constitutional rights,” Walker said in a July 30 statement. “The lawsuit aims to restore the rights of all Michiganders to freely participate in the political process without the threat of government sanction.”

Last April, a three-judge federal panel ordered many of Michigan’s 2010 boundaries redrawn, saying that the Republican-led redistricting plan “represents a political gerrymander of historic proportions” that hurt Democrats and helped the GOP. That partisan redistricting effort resulted in the 2018 initiative that authorized the state’s commission.

That ruling likely will be overturned after the Supreme Court ruled 5-4 in June that the federal courts had no role to play in redistricting.

In California, then-GOP Gov. Arnold Schwarzenegger led the 2008 effort to pass Proposition 11, which created the commission. The majority Democrats opposed the plan, arguing that it would give the redistricting power to unelected state residents.

Editor’s note: An earlier version of this story incorrectly listed who would be banned from becoming members of Michigan’s new state redistricting commission. They include parents, children, spouses, step-children and step-parents of elected or appointed political figures.

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth