A three-judge panel ruled late Tuesday that North Carolina's congressional district map was illegally gerrymandered because of excessive partisanship that gave Republicans a solid advantage for most of the seats.

In a 191-page opinion, judges claimed that the map drawn by Republicans in North Carolina had been "motivated by invidious partisan intent" that would divide the state into 13 districts, of which 10 are Republican.

The federal judges have given state lawmakers until Jan. 29 to fix the issue and show them a new map.

The deadline is important because candidates for the November congressional elections begin filing for the primaries on Feb. 12.

The judges unanimously agreed that the state's lawmakers violated the equal-protection clause in the U.S. Constitution when the state's Republicans drew maps explicitly to favor their party.

The News & Observer in Raleigh, N.C., reports:

"The ruling comes in cases filed by the League of Women Voters and Common Cause in North Carolina stemming from maps adopted in 2016 during a special legislative session. It throws a new wrinkle and more uncertainty into the 2018 election cycle in North Carolina a month before candidates were scheduled to file for office.

"We're enormously gratified on behalf of our clients and all voters in North Carolina that no one will have to endure another congressional election under an unconstitutional map," said Allison Riggs, senior voting rights attorney for the Southern Coalition for Social Justice, which represented some of the challengers. "The court was clear in demanding a real remedy before the 2018 elections, and we expect the General Assembly to respect that order."

Democrats applauded the ruling.

North Carolina Democratic Party Chairman Wayne Goodwin called the ruling 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."

Republicans, however, promise an appeal.

A spokeswoman for Republican state Sen. Ralph Hise, told the Raleigh newspaper that legislative leaders plan to appeal to the U.S. Supreme Court. Hise and state Rep. David Lewis have led redistricting efforts in the legislature.

According to attorney Allison Riggs, the ruling is the first time federal judges have struck down congressional districts as partisan gerrymanders. A Wisconsin case that was argued before the U.S. Supreme Court involved state legislative districts found to be partisan gerrymanders.

NPR's Nina Totenberg reported on the Wisconsin test case before the Supreme Court:

In 2011 Wisconsin Republicans completely controlled the redistricting process for the first time in four decades. A divided federal court later found that Republicans, using high-speed computer technology along with new voter data, were able to draw new district lines to solidify their control of the Legislature for at least the rest of the decade, if not longer.

Indeed, a year after the redistricting, Republicans captured only a minority of the statewide vote — 48.6 percent — but, as they had privately predicted, they still won 60 of the 99 state legislative seats, while the Democrats, who had won a majority of the vote, captured a mere 39 seats.

As the clock ticks down on the North Carolina court order, a majority of the judges agreed that if the legislature won't alter the map, they would hire a redistricting expert to draw replacement boundaries.

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