NEW YORK — A longtime Republican redistricting expert played a key role in adding a citizenship question to the 2020 census, according to court papers filed Thursday by opponents of the move.

The filing in Manhattan federal court said the discovery of new documents revealed that Thomas Hofeller contributed vital language to a letter used to justify adding the question for the first time since 1950.

Lawyers for opponents of adding the question asked a judge to issue sanctions or consider contempt remedies, saying a Justice Department official and a transition official for President Donald Trump testified falsely by hiding Hofeller's role in asking the question.

The new documents may challenge the administration's argument that the citizenship question in the 2020 census is needed to protect minority voting rights. Instead, opponents argue, they show the census change is part of a wider Republican effort to restrict the political power of Democrats and Latino communities.

In their new filing, lawyers said new evidence revealed that Hofeller played a significant role in "orchestrating the addition of the citizenship question ... to create a structural electoral advantage for, in his own words, 'Republicans and Non-Hispanic Whites,' and that defendants obscured his role through affirmative misrepresentations."

The change announced in spring 2018 seems poised for approval by the U.S. Supreme Court, which heard arguments in April and is likely to rule by July.

The Justice Department is planning to file a response in the New York case, said a senior Justice Department official who was not authorized to speak for quotation because the matter is before the courts.

"We were not aware of these documents. The Solicitor General's arguments were based on the record. These were not in the record," the official said.

Lawyers for President Donald Trump's administration say the commerce secretary has wide discretion to design the census questionnaire.

States, cities and rights groups had sued in New York and elsewhere, arguing that the question would suppress the count of immigrants. States with large numbers of immigrants tend to vote Democratic.

Opponents say adding the question will discourage immigrants from participating and strengthen congressional representation and funding for areas where mostly Republicans reside.

Dale Ho, director of the ACLU's voting rights project and a lawyer who argued against adding the citizenship question before the Supreme Court, said documents found after Hofeller's death last year revealed the administration's "goal was to dilute the voting power of minority communities. That's literally the diametric opposite of what the administration has been saying all along."

It's not yet clear if the Hofeller documents might affect the pending Supreme Court case.

"We are considering all options right now," Ho said.

The Hofeller documents cited by lawyers were discovered when his estranged daughter found four external computer hard drives and 18 thumb drives in her father's Raleigh, North Carolina, home after his death last summer.

The New York Times reported that she contacted Common Cause, which had recently sued in state court to challenge North Carolina's legislative districts which had been drawn by Hofeller.

On Thursday, Common Cause President Karen Hobert Flynn said in a release that documents revealed "that the plan to add the citizenship question was hatched by the Republicans' chief redistricting mastermind to create an electoral advantage for Republicans and non-Hispanic whites."

She said the documents contradict testimony by administration officials that they sought to add the question to benefit Latino voters.

In New York, U.S. District Judge Jesse M. Furman set a hearing for June 5.

Furman ruled in January that the question could not be included on the census, saying fewer people would respond to the census and that the process used to add it was faulty.

Besides the citizenship question, the Supreme Court also is expected to rule within weeks whether North Carolina and Maryland can set limits for the first time on drawing districts for partisan advantage.

Sherman reported from Washington. Associated Press Writer Emery P. Dalesio in Raleigh, North Carolina, also contributed to this report.