A group of Republicans has sued the Michigan redistricting commission over its recently-approved congressional map, claiming the panel failed to draw districts with equal populations.

The lawsuit, filed Thursday with the U.S. District Court for the Western District of Michigan, also names Michigan Secretary of State Jocelyn Benson as a defendant.

The plaintiffs claim the map “fragments counties, townships, and municipalities” without a necessary reason. The suit seeks an order to redraw the maps, which are expected to take effect in March.

Among the seven Republican plaintiffs are Rep. Beau LaFave, R-Iron Mountain, and former Rep. Joseph Graves, R-Linden. LaFave is also running for secretary of state.

According to the U.S. Constitution, each congressional district must have about the same population. Based on the 2020 Census, that means that each district in Michigan should be as close to 775,179 people as possible per each of the 13 congressional districts.

Last month, the Michigan Independent Citizens Redistricting Commission approved the new state legislative and congressional maps. But the congressional map — nicknamed  the Chestnut —  has districts with a population deviation larger than allowed, according to the lawsuit.

The largest congressional district, the 13th that includes Detroit, has 487 more people than the target number. Meanwhile, the 5th District, which extends from New Buffalo east to Monroe, is 635 people below the population target.

The state’s redistricting commission followed a constitutional-ranked criteria when it drew the map. The first criterion establishes “districts shall be of equal population.”

“The Commissioners’ failure to create districts with equal population also suggests that they did not prioritize the criteria enumerated in the Michigan Constitution in the order mandated by the Michigan Constitution,” the lawsuit said.

A Bridge Michigan analysis found that the congressional map would give Democrats an advantage in 7 of 13 districts. The delegation is now split 7-7, but Michigan is losing a seat due to stagnant population.

Edward Woods III, a spokesperson for the commission, said in an email that “seeing that this lawsuit reflects pending litigation, the MICRC will acknowledge that we followed the seven ranked redistricting criteria stated in Michigan’s constitution.”

The lawsuit also claims that 15 of Michigan’s 83 counties are split among districts. Parts of Oakland County are split into six congressional districts.

“The boundaries established by the Commissioners are arbitrary, inconsistent, and non-neutral” with the U.S. Constitution, the lawsuit said.

This is the latest lawsuit to be filed against the Michigan Independent Citizens Redistricting Commission, which was created by voters in 2018 to replace a decades-long system that allowed the party in power to draw legislative boundaries every ten years after the decennial census.

Earlier this month, the Detroit caucus of the state Legislature and Black leaders from the city filed a lawsuit against the commission with the Michigan Supreme Court.

That lawsuit claims all three maps approved by the commission dilutes the Black voting power in the state because it diminishes the number of majority-Black districts.