WASHINGTON (AP) — The Supreme Court on Wednesday threw out Wisconsin state legislative maps that were preferred by the state's Democratic governor and selected by Wisconsin's top court, making it unclear what the boundaries will be for the fall election.

But while the justices in an unsigned opinion threw out voting maps the Wisconsin Supreme Court had selected for the State Assembly and Senate, they left in place state congressional maps. The state's highest court selected the maps from a range of options after lawmakers and the governor couldn't agree.

Republicans had complained that Gov. Tony Evers' maps moved too many people to increase the number of Assembly districts with a majority of Black and Hispanic voters from six to seven in violation of the federal Voting Rights Act.

The Wisconsin Supreme Court ruled 4-3 in favor of adopting Evers' maps earlier this month, with a conservative justice joining three liberals in the majority. Republicans immediately appealed to the U.S. Supreme Court, arguing that the maps drawn by Evers were racially gerrymandered.

The Wisconsin Supreme Court failed to consider whether a "race-neutral alternative that did not add a seventh majority-black district would deny black voters equal political opportunity," the Supreme Court said. The analysis done by the Wisconsin Supreme Court did not adhere to U.S. Supreme Court precedents "and its judgment cannot stand," the nation's high court said.

The justices sent the case back to the Wisconsin Supreme Court, saying it is "free to take additional evidence if it prefers to reconsider the Governor's maps rather than choose from among the other submissions." They said their action would give Wisconsin's high court "sufficient time to adopt maps" in time for the state's Aug. 9 primary.

The decision throws into question whether candidates will be able to begin circulating nomination papers as scheduled on April 15 given that new district boundaries aren't set. The Wisconsin Elections Commission, which administers elections, did not immediately return a message.

Sachin Chheda, director of the Fair Elections Project, said the ruling throws Wisconsin's legislative elections into "chaos" just three weeks before nomination papers can be circulated.

"Never has it been clearer that the US Supreme Court majority will do anything it can to advance Republican interests, rather than the law, the Constitution, and the will of the people," Chheda said.

Two justices, Sonia Sotomayor and Elena Kagan, said they disagreed with their colleagues' decision.

"I would allow that process to unfold, rather than further complicating these proceedings with legal confusion," Sotomayor wrote.

The Legislature redraws Wisconsin's congressional and legislative district maps every 10 years to reflect population changes. The process, known as redistricting, can solidify the partisan majority in the Legislature for a decade. With the stakes so high, Evers and Republican lawmakers couldn't agree on a plan, leading to both sides asking the state Supreme Court to choose between each side's maps.

Democrats would have made some marginal gains under Evers' plan but Republicans would maintain their majorities in the Assembly and Senate, according to an analysis from the governor's office. Currently, Republicans hold a 61-38 majority in the Assembly and a 21-12 advantage in the Senate.

Republicans currently hold five of the state's eight congressional districts. The new map upheld by the court would make the southeastern Wisconsin district held by Republican Rep. Bryan Steil more competitive.

In 2018, Democrats won every statewide race but Republicans held more than 60% of legislative seats. Republicans blamed bad Democratic candidates, in part, while Democrats argued that gerrymandering enshrined the GOP advantage.

The Wisconsin Supreme Court ruled 4-3 in favor of adopting Evers' maps earlier this month. Republicans immediately appealed to the U.S. Supreme Court, arguing that the maps drawn by Evers were racially gerrymandered.

Wisconsin's Democratic Attorney General Josh Kaul, who defended Evers, called the Supreme Court's ruling "shocking" and consistent with "increasing activism" from the conservative majority on the court.

"It's now created massive uncertainty going forward," Kaul said. "We're going back to the drawing board on this and I think there's going to be a lot of litigation ahead."

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Associated Press writer Todd Richmond contributed to this report. Bauer and Richmond reported from Madison, Wisconsin