Civil rights groups and Ohio voters filed a lawsuit Wednesday challenging the state’s congressional districts as unconstitutional, as the Supreme Court readies decisions in similar cases about whether maps can be rejected if they entrench an advantage for one party.

The lawsuit, filed by the American Civil Liberties Union in U.S. District Court in Cincinnati, seeks a new congressional map for Ohio. But it almost certainly comes too late in the 2018 election cycle to affect districts ahead of the November vote. Ohio already held its primary election under the current map on May 8.

The legal claims echo those in pending Supreme Court cases on partisan gerrymandering, meaning the lawsuit’s fate likely rests on what the high court decides before its term ends in June.

The Ohio legal fight will play out during what could be a critical time, when voters across the country choose which party will control state offices ahead of redistricting based on the 2020 census.

In Ohio, however, the potential bite of partisan gerrymandering in that process got reduced when state voters in May overwhelmingly approved a ballot proposal that requires bipartisan cooperation in drawing new congressional districts.

Watch: The Many Ways to Draw a Gerrymander

In the lawsuit, Ohio voters argue that the state’s congressional map, drawn by Republicans after the 2010 census, locked in a 12-4 advantage for the GOP that infringes on voters’ rights to choose their representatives.

Republicans in Ohio received 51 percent to 59 percent of the statewide vote in congressional elections, yet consistently won 75 percent of the congressional seats, the lawsuit states.

“This 12-4 map prevents large portions of Ohio’s voting population from ever having their votes meaningfully deployed to count, much less see their democratic will reflected, in their congressional delegation,” the lawsuit states.

To show how the map favors Republicans, the lawsuit highlights the “highly irregular, sprawling shapes” of seven congressional districts. The voters argue that the boundary lines concentrate Democrats into just four districts — a practice known as “packing” — to reduce their power in the state.

These Democratic-held seats are the 3rd District held by Rep. Joyce Beatty, which the voting groups say in the lawsuit is “shaped like a snowflake,” and the 9th District held by Rep. Marcy Kaptur that is known as “the Snake on the Lake.”

There is also the 11th District held by Rep. Marcia L. Fudge that “resembles a detached shoulder blade with a robotic arm that reaches out from a shoulder of Cleveland,” and the 13th District held by Rep. Tim Ryan that is a “jigsaw puzzle piece.”

And the lawsuit highlights Republican-held districts that split Democratic voters to dilute their votes in a practice known as “cracking.” Those are the 1st District held by Rep. Steve Chabot, the 4th District represented by Rep. Jim Jordan, and the 16th District held by Rep. James B. Renacci.

“Both tactics force the votes of those from the opposing party to be used inefficiently, by placing the opposing party’s voters in districts where their votes will not have any impact on the outcome,” the lawsuit states.

At the high court

The Supreme Court grappled with two cases this term that made similar arguments. While the high court has never decided that federal courts can hear challenges to a state’s political maps on the basis of partisan gerrymandering, it hasn’t ruled it out either.

One case focuses on Wisconsin’s statehouse map, and the other deals with a Maryland congressional district, but both could have national implications depending on how the justices rule. A similar challenge to North Carolina’s congressional districts is on hold pending the high court’s decision.

Ohio Gov. John Kasich, a Republican who is a defendant in the new lawsuit, signed on to a brief in one of the Supreme Court cases that argued partisan gerrymanders are unconstitutional, “are harming our republican government, and readily can be identified and addressed by courts.”

Ohio Secretary of State Jon Husted, also named as a defendant in the lawsuit, questioned the timing.

“If the way the congressional lines were drawn was such an issue for the ACLU, A. Philip Randolph Institute and League of Women Voters, why did they wait six years to file a lawsuit challenging the maps?” Husted said in a news release. “These groups should respect the will of Ohio’s voters who overwhelmingly approved a constitutional amendment earlier this month that established a new, bipartisan process for drawing congressional districts starting in 2021.”

Under Ohio’s recently approved ballot measure, new maps would require support from at least half the members of the minority party and three-fifths support in Ohio’s House and Senate overall. If the Legislature can’t agree on a map, a seven-member bipartisan commission, with members appointed by state lawmakers, would draw the new maps.

The new lawsuit challenges Ohio’s map under the U.S. Constitution, making it different from a recent partisan gerrymandering challenge in Pennsylvania that redrew the Keystone State’s map ahead of this year’s election.

The Pennsylvania Supreme Court struck down that state’s GOP-drawn congressional map on a pioneering ruling that said it violated the state’s constitution because it solidified an advantage for Republicans.

Pennsylvania Republicans have won 13 of the state’s 18 House seats in the last three elections, but the new map is less favorable to them.

The Ohio case is A. Philip Randolph Institute v. Kasich, Docket No. 18-cv-00357. It was filed in the U.S. District Court for the Southern District of Ohio.

Robin Opsahl contributed to this report.