(CNN) In a blow to the Trump administration, a federal trial judge said Wednesday that he believes new evidence presented in a challenge to the 2020 census citizenship question "raises a substantial issue."

The decision could lead to reopening one of three federal trials into the citizenship question and lead to further examinations of Republican redistricting consultant Thomas Hofeller's role in developing the question.

Earlier this month, the ACLU and a team of lawyers at Arnold & Porter said that they had obtained a trove of documents from Hofeller, a deceased Republican redistricting expert who, they allege, played a significant role in the decision to add the question. Hofeller wrote a study in 2015 concluding that using "citizen voting age" population as the redistricting population base would be "advantageous to Republicans and Non-Hispanic Whites."

The administration has always denied political motivation, saying instead that the Justice Department had determined that the question was necessary to better comply with federal voting rights law.

Judge George Hazel of the US District Court in Maryland disagreed with the government's arguments that Hofeller's files were "not material and it would not produce a new outcome."

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