The long fight to end partisan gerrymandering moved a critical step closer to victory today as a three-judge federal court ruled that Wisconsin lawmakers must act this year to revise state assembly districts that the court believes were drawn to give Republican candidates a lopsided advantage.

The 2-1 decision puts the case on a direct path to the Supreme Court, which has never overturned a redistricting plan based on its partisan leanings. Similar challenges to partisan gerrymanders are pending in federal courts in Maryland and North Carolina; Common Cause is a plaintiff in the North Carolina case and the Maryland challenge was brought by Steve Shapiro, a Common Cause activist.

The majority in the Wisconsin case concluded last November that state assembly districts drawn by the Republican-led legislature violate the First Amendment and the Equal Protection clause of the Constitution. Those provisions “prohibit a redistricting scheme which (1) is intended to place a severe impediment on the effectiveness of the votes of individual citizens on the basis of their political affiliation, (2) has that effect, and (3) cannot be justified on other, legitimate legislative grounds,” the judges said.

The court on Friday gave Wisconsin legislators until Nov. 1 to devise and adopt a revised legislative map; the judges refused a to take on the mapmaking themselves. The deadline means new districts will be in place in time for the 2018 midterm election, unless the Supreme Court intervenes.