Since announcing its decision to add a citizenship question to the 2020 Census, the Trump administration has been fighting to obscure its reasoning for doing so. In half a dozen ongoing lawsuits against the administration, White House lawyers have sought to suppress memos, notes, and other evidence related to its last-minute decision.

On Friday, a federal judge denied another effort to delay testimony by a key witness, calling the request “frivolous.”

A quick refresher on how we got here. In March, Commerce secretary Wilbur Ross announced that the Census Bureau would be asking every person in the United States whether they are a citizen. In a memo, Secretary Ross said the question was necessary to improve enforcement of the Voting Rights Act. That decision ignored the judgment of six former census directors and the Census Bureau’s own chief scientists—all of whom agreed that the new question, added without proper testing, would undermine the accuracy of the 2020 count.

Gore’s testimony is crucial because it was Gore who allegedly “ghost wrote” the letter from the Department of Justice (DOJ) requesting that a citizenship question be added to the census.

Almost immediately, some seventeen states, the District of Columbia, cities, and coalitions of civil society groups sued the Trump administration, alleging that the decision violated the Administrative Procedures Act, which prohibits federal agencies from taking “arbitrary” or “capricious” action. Rather than a good-faith effort to improve reporting, plaintiffs alleged, the decision was a deliberate and malicious effort to sabotage the count to gain partisan advantage.

Judge Jesse Furman’s decision Friday denied the Trump administration’s request to block the deposition of a key player in this saga: acting assistant attorney general for civil rights John Gore. Gore’s testimony is crucial because it was Gore who allegedly “ghost wrote” the letter from the Department of Justice (DOJ) requesting that a citizenship question be added to the census. And its that letter which is the basis for the Commerce Department’s claim that their reasoning for reinstating the citizenship question was the DOJ’s need for better enforcement of the Voting Rights Act.

It’s no mystery why the White House wants to keep Gore from testifying under oath. Emails disclosed earlier in the litigation process reveal that Ross had asked his deputy, Earl Comstock, about adding a citizenship question almost as soon as Trump was inaugurated. In one email, Comstock informs Ross, “We will need to work with Justice to get them to request that citizenship be added back as a census question.”

The emails undermine the White House timeline, in which Ross responds to the DOJ request (authored by Gore), goes through a deliberative process, and elects to add a citizenship question. Instead, the emails suggest that it was always the Trump administration’s intention to include a citizenship question; they sought out the DOJ to provide a post hoc justification.

Naturally, the plaintiffs in the census suit have a lot of questions for John Gore. Judge Furman acknowledged as much.

“Put simply,” Furman wrote in his decision, “a deposition of the person who apparently wrote the memorandum that Secretary Ross himself requested and then later relied on to justify his decision to add the citizenship question is highly relevant ‘to assessing the commerce secretary’s reasons.’”

And unless the administration can come up with another “frivolous” excuse, Gore will be deposed, as planned, on Wednesday, September 12.