Republican Sens. Bob Rucho, left, and Phil Berger talk during a session of the North Carolina Senate in Raleigh in 2016. (Corey Lowenstein/News & Observer/AP)

A federal court on Tuesday ruled that Republicans in North Carolina unconstitutionally gerrymandered congressional districts in 2016 to ensure Republican “domination of the state’s congressional delegation.”

The three-judge panel struck down the map and ordered the state’s General Assembly to come up with a substitute by Jan. 24.

The decision was the first striking down of a congressional map, as opposed to a state legislative map, on the grounds that it was rigged in favor of a particular political party. Redistricting has historically been political and partisan to one degree or another.

While courts have invalidated redistricting plans, including ones in North Carolina, as racially discriminatory, judicial objection to gerrymandering for partisan gain is relatively new territory, with legal standards unsettled by the U.S. Supreme Court. Indeed, the court has never struck down a redistricting plan on the basis of partisan gerrymandering.

The process of redrawing district lines to give an advantage to one party over another is called "gerrymandering." Here's how it works. (Daron Taylor/The Washington Post)

Two cases currently under consideration by the high court, one from Wisconsin and another from Maryland, may provide guidance. If North Carolina appeals Tuesday’s decision, the Supreme Court could very well add that case to its docket.

The dilemma for the court, as Chief Justice John G. Roberts Jr. said during October’s oral arguments in the Wisconsin case, Gill v Whitford, is that adjudicating partisan gerrymandering cases will flood the courts.

“Politics is a very important driving force” in redistricting, he said, “and those claims will be raised. And every one of them will come here for a decision on the merits. … We will have to decide in every case whether the Democrats win or the Republicans win.” However the court rules will be perceived as partisan, he added, “and that is going to cause very serious harm to the status and integrity of the decisions of this court in the eyes of the country.”

Tuesday’s decision was made easier for the panel by a kind of smoking gun: Republican leaders in the North Carolina General Assembly openly conceded that the 2016 map was drawn to benefit Republicans.

They hired a consultant from the Republican National Committee to draw the map and excluded Democrats from the process, the court panel said. That consultant, the court said, testified that he was told “to minimize the number of districts in which Democrats would have an opportunity to elect a Democratic candidate.”

“Rather than seeking to advance any democratic or constitutional interest,” the panel wrote in a lengthy opinion, “the state legislator responsible for drawing the 2016 plan,” Rep. David Lewis, openly declared that he drew the map to advantage Republican candidates because he thinks “electing Republicans is better than electing Democrats.”

But that, said the panel, “is not a choice the Constitution allows legislative mapdrawers to make.”

The Republican-dominated House and Senate in North Carolina set out to entrench Republicans and succeeded in doing so, the panel declared. The plan was designed to give Republicans victories in 10 of the state’s 13 districts, and did just that.

Rendering the decision were Judge James A. Wynn, an appointee of President Barack Obama to the U.S. Court of Appeals for the 4th Circuit, and U.S. District Court judges W. Earl Britt, a Jimmy Carter appointee, and William L. Osteen Jr., a George W. Bush appointee.

The panel found violations of three separate constitutional provisions.

The General Assembly violated the Equal Protection Clause, the panel said, “because the General Assembly enacted the plan with the intent of discriminating against voters who favored non-Republican candidates” and the plan “has had and likely will continue to have that effect,” which it said is not justified by any “legitimate state interest.”

Second, the panel said the partisan gerrymandering violated the First Amendment “by unjustifiably discriminating against voters based on their previous political expression and affiliation.” Osteen dissented from that portion of the opinion but otherwise concurred.

And finally, the panel said the gerrymandering violated the provisions of Article I of the Constitution, which gives states the power to draw up congressional districts, “by exceeding the scope of the General Assembly’s delegated authority to enact congressional regulations and interfering with the right of ‘the People’ to choose their Representatives.”

The plan “has discriminated, and will continue to discriminate, against voters who support non-Republican candidates,” wrote Wynn for the court.

Leaders of the Republican legislature plan to appeal to the Supreme Court, the Raleigh News and Observer reported.

Dallas Woodhouse, executive director of the North Carolina Republican Party, sent out a tweet personally criticizing Wynn for “waging a personal, partisan war on North Carolina Republicans.”

“Once again,” he added, “unaccountable federal judges are attempting to throw North Carolina’s elections into chaos by adopting radical, untested new theories at the eleventh hour. This must be appealed.”

The state’s Democratic Party chairman, Wayne Goodwin, in a statement published by the News and Observer, called the decision a “major victory for North Carolina and people across the state whose voices were silenced by Republicans’ unconstitutional attempts to rig the system to their partisan advantage.”

The redistricting plan was challenged in court by Common Cause, the League of Women Voters of North Carolina as well as individual voters in the state.

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