When a group of Pennsylvania voters successfully won their challenge last year to the state’s gerrymandered congressional map, it was a seismic event for the legal and political establishment.

An aftershock just rocked North Carolina.

A panel of state judges there ruled Tuesday that the state legislative maps violate the North Carolina Constitution. As in Pennsylvania, the court relied solely on the state constitution to throw out the existing political boundaries; also like in Pennsylvania, expert witnesses demonstrated how the map was highly favorable to Republicans, going far beyond what would occur in a politically neutral mapping.

The similarities were no accident. The two cases are “very closely connected” because the Pennsylvania case was a model for the North Carolina one, said R. Stanton Jones, a Washington-based lawyer who was involved in both. After winning here, Jones said, the legal team began looking at other states.

“We began to think about and look at places where we could replicate, where we could employ the same strategy to solve the problem of partisan gerrymandering,” he said Wednesday.

After the U.S. Supreme Court ruled in late June that federal courts couldn’t touch the issue of partisan gerrymandering — the practice of drawing political lines to unfairly favor one party — experts said the Pennsylvania case would be a model for how maps could be challenged in state courts.

» READ MORE: U.S. Supreme Court: Partisan gerrymandering is a political issue that federal courts can’t touch

“The decisions from both the Pennsylvania Supreme Court last year and [Tuesday’s]decision from the North Carolina court should serve as a warning to state legislatures that might otherwise be interested in trying to gerrymander congressional or state legislative districts for partisan gain in 2021,” said Jones.

The North Carolina case

All three state judges — two Democrats and a Republican — agreed that North Carolina’s state House and Senate maps violated the state’s constitution by being so unfairly skewed toward Republicans that voters did not have fair and representative elections, and were essentially punished if they associated with the Democratic Party.

The judges said the political maps violated the state constitution’s guarantees of free elections, freedom of assembly, freedom of speech, and equal protection under law.

The maps were drawn by the Republican-controlled legislature in 2017, after the previous maps were ruled unconstitutional. This time, the court gave the legislature two weeks to draw new ones, forbade the use of “partisan considerations and election results data," and ordered the mapmaking process to be conducted in “full public view.”

If the legislature fails to come up with a suitable map, the judges wrote, they might reschedule the 2020 primary elections.

The elections clause that was key to the Pa. and N.C. cases

The courts found that in both states the gerrymandered maps violated constitutional language regarding elections:

Elections shall be free and equal; and no power, civil or military, shall at any time interfere to prevent the free exercise of the right of suffrage.
Pennsylvania Constitution (Article I, Section 5)
All elections shall be free.
North Carolina Constitution (Article I, Section 10)

The North Carolina judges traced the clause back to the 1689 English Bill of Rights, noting that multiple states, including Pennsylvania, had versions of a free election clause in their state constitutions.

These provisions make state constitutions broader in their protections than the federal Constitution, said Joshua A. Douglas, a law professor at the University of Kentucky. Thus they are tools for challenging unfair political maps, as they were in Pennsylvania and North Carolina.

“So I think the cases are absolutely parallel and provide a good model for other courts moving forward,” he said.

» READ MORE: Why Pa.'s gerrymandered map went too far, acccording to state Supreme Court

About half the state constitutions have similar clauses, and courts in those states could similarly interpret the language to find extreme partisan gerrymanders unconstitutional, Douglas said.

“Elections are not free when partisan actors have tainted future elections by specifically and systematically designing the contours of the election districts for partisan purposes and a desire to preserve power,” the North Carolina judges said.

What happens next with the Pa. anti-gerrymandering model

Experts and lawyers on all sides agreed that more state court challenges are likely.

“They certainly followed their Pennsylvania playbook in North Carolina,” said Jason Torchinsky, a prominent Republican elections lawyer who defended Pennsylvania Republicans in last year’s case and serves as general counsel to the National Republican Redistricting Trust.

» READ MORE: Pennsylvania's congressional map fight reveals a deeper national redistricting battle

He accused Democrats, who are often concentrated in urban areas, of using the courts to overcome their geographic disadvantage. They also waited, he said, until both states had Democratic majorities on their state Supreme Courts.

(The Pennsylvania and North Carolina maps favored Republicans beyond what geography could reasonably account for, according to various analyses. And lawyers for the challengers have said they needed to wait multiple election cycles to demonstrate how the maps play out in real election results.)

Skewed maps are being used in Wisconsin and Maryland, among other states, but it’s impossible to know when the next suits will be filed. It’s late in the redistricting cycle: Maps are redrawn every 10 years, after the census. But experts said lawmakers now know that legal challenges are realistic threats if they draw extremely gerrymandered maps in 2021.

“They’ve never really had much of a strong threat of this before, so without any sort of disincentive for skewing districts, you see how they’ve taken that as kind of a green light,” said Dan Vicuña, national redistricting manager for Common Cause, the good-government group whose North Carolina branch was among the plaintiffs. “If it turns out that legislators are not scared by what they see in the state courts, then we’ll look at suing and shaming them and using everything in our toolbox.”

» READ MORE: Pennsylvania, gerrymandered: A guide to Pa.’s congressional map redistricting fight