In an ideologically split 4-3 decision, the Wisconsin Supreme Court ruled Friday that the state’s electoral maps, which were gerrymandered over a decade ago to favor Republicans, were unconstitutional, setting up a redrawing of the maps in advance of the 2024 election in the crucial presidential swing state.

The court’s majority said that over half of the state assembly’s 99 districts, and at least 20 of its 33 Senate districts, violated the state’s constitutional requirement for districts to be made of “contiguous territory.”

“Given the language in the Constitution, the question before us is straightforward,” wrote Justice Jill J. Karofsky in the majority decision. “When legislative districts are composed of separate, detached parts, do they consist of ‘contiguous territory’? We conclude that they do not.”

The GOP-favored maps, first drawn in 2011 when Scott Walker took over the state’s governorship and reinforced in 2022 when conservatives controlled the state’s highest court, have given the Republican Party a stranglehold in the Wisconsin legislature.

The GOP holds a 64-35 majority in the state assembly and a 22-11 majority in the state senate, even as the state’s electorate remained deeply split in recent presidential elections. In 2020, the state broke for Joe Biden by just over 20,000 votes.

The decision was praised by Wisconsin’s Democratic governor, Tony Evers. “Wisconsin is a purple state, and I look forward to submitting maps to the Court to consider and review that reflect and represent the makeup of our state,” Evers said in a statement. “And I remain as optimistic as ever that, at long last, the gerrymandered maps Wisconsinites have endured for years might soon be history.”

Robin Vos, a Republican and the Speaker of the Wisconsin Assembly, argued that “the case was pre-decided before it was even brought.” Vos added: “[It's a] sad day for our state when the State Supreme Court just said last year that the existing lines are constitutional. The U.S. Supreme Court will have the last word.”

Lawmakers must draw up new maps by mid-March 2024, but with time running out, the court’s majority said if the two parties fail to agree, the court would step in and create constitutional maps that would not advantage either Republicans or Democrats.

The decision reflects the momentous right-to-left swing the court has undergone in the last year. In April, current liberal Justice Janet Protasiewicz beat a far-right candidate in the most expensive court election in U.S. history, shifting the court from conservative to liberal control. 

During her campaign, Protasiewicz had described the state’s electoral maps as “unfair” and “rigged,” leading some GOP officials, led by Vos, to call for her impeachment if she ruled in favor of redrawing the districts.

Protasiewicz did rule for the majority, but Vos had already appeared to back off on Wednesday. “[Impeachment is] one of the tools that we have in our toolbox that we could use at any time,” he said in an interview. “Is it going to be used? I think it’s super unlikely.”