(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."

His order allows the groups suing the government -- alleging the question was developed with discriminatory intent and amounted to an illegal conspiracy -- to ask an appeals court to remand the case to his lower court.

The original Maryland trial, like those in New York and California, resulted in orders blocking the question from appearing on the census.

But the judge in Maryland ruled the plaintiffs had not proved that the government acted with discriminatory intent when in adding the question. Like in the other trials, Hazel said Commerce Secretary Wilbur Ross' motives were unclear.

Plaintiffs believe the new evidence could sway that aspect in their favor.

The Supreme Court is expected to rule soon on two other cases challenging the citizenship question. Plaintiffs in the Maryland case note that their case brings up issues that were not discussed in the cases heard in New York or California, and believe their challenge may proceed separately from matters before the Supreme Court.

Denise Hulett, an attorney for one of the plaintiffs -- the Mexican American Legal Defense and Educational Fund, or MALDEF -- who argued at a court hearing Tuesday, said the next step is for the appeals court to decide whether it will return the case to the trial court.

If the case is remanded, Hazel has several options: He could order more discovery, additional subpoenas, testimony or exchange of documents, Hulett said. He could also decide he has enough information and rule based on the newfound evidence alone.

"What happens if the 4th Circuit remands, we'll wait for some indication in Judge Hazel's opinion," Hulett told CNN.

Hazel told the courtroom that, at trial, he was 49% of the way to finding in favor of the plaintiffs on their claim of intentional discrimination.