Three federal judges ruled that Michigan must redraw at least 34 congressional and legislative districts before the 2020 election.

The judges said the 2011 Republican-led redistricting effort elevated "partisan considerations" at every step.

Visit Business Insider's homepage for more stories.

LANSING, Mich. (AP) — A three-judge federal panel ruled Thursday that Michigan's congressional and legislative maps are unconstitutionally gerrymandered, ordering the state Legislature to redraw at least 34 districts for the 2020 election.

The decision also requires special state Senate elections to be held in 2020, instead of 2022 as scheduled.

The judges said 34 of the 162 congressional and legislative districts drawn by Republicans in 2011 violate Democratic voters' constitutional rights, including by diluting the weight of their votes. They gave the GOP-led Legislature until Aug. 1 to submit new maps, which would need the signature of Democratic Gov. Gretchen Whitmer. An appeal is likely.

Voters at a voting place for the midterm election in Detroit, Michigan, November 6, 2018. REUTERS/Rebecca Cook

The federal panel — Judge Eric Clay of the 6th US Circuit Court of Appeals, US District Judge Denise Page Hood of Michigan's eastern district and US District Judge Gordon Quist of Michigan's western district — said those involved in the 2011 redistricting effort elevated "partisan considerations" at every step.

"Their primary goal was to draw maps that advantaged Republicans, disadvantaged Democrats, and ensured that Republicans could enjoy durable majorities in Michigan's congressional delegation and in both chambers of the Michigan legislature for the entire decade," the judges wrote.

The ruling came in a lawsuit filed by the League of Women Voters of Michigan and Democratic voters who claimed districts were shaped by Republican operatives to guarantee the party's dominance in the state Capitol after the 2010 census. They said constitutional rights were violated when Democratic areas were packed in certain districts or diluted elsewhere.

GOP lawmakers who intervened in the suit have said the entire proceeding should be halted until the US Supreme Court rules on redistricting cases from North Carolina and Maryland.