RALEIGH, N.C. (Reuters) - North Carolina’s state legislative districts were unconstitutionally gerrymandered to entrench Republicans in power and must be thrown out, a lawyer for state Democrats and a good-government advocacy group told a panel of judges on Monday.

FILE PHOTO: FILE PHOTO: A worker holds stickers for voters at a polling station at the Princeton Baptist Church during the U.S. presidential election, in Princeton, North Carolina, U.S. November 8, 2016. REUTERS/Chris Keane/File Photo/File Photo

The case is the first to reach trial since the U.S. Supreme Court ruled last month that federal courts have no authority to curb partisan gerrymandering, the practice of drawing electoral maps to benefit one political party over another.

The decision did not prevent state courts from taking up the issue based on state constitutions, a legal avenue that advocates have said they will vigorously pursue.

“Republicans in the General Assembly have manipulated the district lines to guarantee that their party will control both the state House and the state Senate, regardless of how people vote,” attorney R. Stanton Jones said as the civil trial began in Superior Court in Raleigh, the state capital.

“This attack on representative democracy and voting rights is fundamentally unfair.”

A lawyer for Republican lawmakers, Phillip Strach, said Democrats were using the court to sidestep the electoral and legislative processes.

“This lawsuit is not about protecting democracy,” Strach said. “It is a full, frontal assault on democracy.”

Last year, the Pennsylvania Supreme Court struck down that state’s congressional map as an illegal Republican gerrymander. Gerrymandering critics have said they hope a second victory in North Carolina could bolster similar efforts around the country.

While the latest case does not specifically address the Southern state’s congressional districts, a ruling outlawing partisan gerrymandering would likely also apply to federal lines.

A win for the plaintiffs would improve Democrats’ fortunes in next year’s state legislative elections, after years of Republican control. The party in power will control the next round of redistricting for both U.S. congressional and state legislative maps in 2021.

Despite losing the statewide popular vote, Republicans won a majority of seats in both houses of the state legislature last year.

“The simple truth is this: because of the extreme gerrymandering, Democrats cannot win a majority in the House or the Senate under the 2017 map,” said Jones, the plaintiffs’ lawyer.

Strach countered that constitutional requirements, such as keeping counties undivided, leave little room for partisan manipulation. Democratic voters’ natural tendency to cluster in urban areas is more responsible for the party’s lack of success, he said.

Much of the trial testimony will likely center on the work of Thomas Hofeller, the recently deceased consultant who drew the maps in question. Common Cause obtained thousands of documents from Hofeller’s estranged daughter that Jones said prove “beyond a doubt that partisan gain was his singular objective.”

The Hofeller files also played a role in the recent legal fight over the Trump administration’s effort to add a citizenship question to the U.S. census, after some documents showed Hofeller authored a study concluding doing so would benefit Republican gerrymandering efforts.

Strach said Hofeller was a “boogeyman” used by the plaintiffs to distract from their weak case.

The case is expected to end up before the state Supreme Court, where Democratic judges hold six of the seven seats.