Deceased Strategist’s Files Detail Republican Gerrymandering in North Carolina, Advocates Say

The latest evidence presages what could be a furious battle involving voting-rights advocates, the two national parties, and even Mr. Hofeller’s heirs, over whether any other secrets on the storage drives will ever see the light of day.

The court filing by Common Cause on Thursday included a letter sent by lawyers for Republican legislative leaders, demanding that lawyers for Common Cause return Mr. Hofeller’s hard drives to his estate and destroy any information that had been copied from them. The demand was issued one day after documents from the Hofeller files surfaced in the litigation over the census citizenship question.

Stephanie Hofeller, the strategist’s daughter, said in a telephone interview that since then, she had come under pressure from allies of her father to keep the remaining content of the hard drives private. She declined to elaborate, beyond saying that the disclosure of the census-related documents had upset them.

She said the pressure had only stiffened her resolve. “They’ve underestimated me,” she said.

The disclosures on Thursday came a week after other documents from the storage drives showed that Mr. Hofeller had been involved in the Trump administration’s plans to add a citizenship question to the 2020 census — and that he had written earlier about how data from such a question could be used to dilute the political power of Hispanic voters and Democrats during redistricting.

During a long career, Mr. Hofeller helped Republican politicians across the country draw political maps in their favor after censuses, a practice known as gerrymandering. He was an architect of a spectacularly successful plan by national Republican officials to dominate state governments and the House of Representatives in this decade by taking control of the state legislatures that draw and approve those maps.

Virtually no public record of Mr. Hofeller’s work on gerrymanders exists beyond the maps themselves, because he was obsessive about leaving no paper trail that could be used against his handiwork in court.

Eight years after the last round of redistricting, there are few if any other active court challenges to gerrymanders that could be affected by documents on Mr. Hofeller’s storage drives. The Supreme Court is expected to rule by the end of June on one of them, the federal court’s decision that a map of North Carolina’s House of Representatives districts, drawn by Mr. Hofeller, is an unconstitutional partisan gerrymander.