President Trump asserted executive privilege over key documents related to the administration’s effort to add a citizenship question to the census, the Department of Justice said Wednesday morning.

The documents had been subpoenaed by the House Oversight Committee in April. The announcement of the invocation of executive privilege came just as the committee was beginning a meeting to vote on recommending that Attorney General Bill Barr and Commerce Secretary Wilbur Ross be held in contempt for defying the subpoena.

The documents that Democrats have prioritized have to do with how the administration came up with the official reason it offered for adding the citizenship question: allegedly to enhance DOJ enforcement of the Voting Rights Act. Other internal documents that have been released have made clear that Ross was pressuring aides to add the question well before the VRA justification was put forward, and three federal courts have called the rationale pretextual.

Cummings addressed the assertion of privilege Wednesday at the committee meeting ahead of the contempt vote.

“This begs the question: what is being hidden?” Cummings said.

The Justice Department had warned Tuesday afternoon it would seek an executive privilege assertion unless Oversight Committee Chairman Elijah Cummings held off on the contempt vote. Cummings responded in a letter Tuesday evening that offered to let the Justice Department turn over some of the subpoenaed docs Tuesday night in exchange for postponing the contempt vote.

The Justice Department has claimed that the subpoenaed documents it’s withholding are covered either by deliberative process privilege, attorney-client communications privilege, or attorney work product components of executive privilege. The Justice Department has noted that courts have allowed the administration to withhold the documents in the civil litigation around adding the question.

Whether the question stays on the 2020 census will be decided by the Supreme Court, likely by the end of the month.

Republicans have accused Democrats on the committee of seeking to “influence” the Supreme Court in its investigation into why the question was added to the census. They also argued that the fact that the Commerce Department was still letting its officials sit for interviews with the committee proved that the administration wasn’t stonewalling the investigation.

On Wednesday, the Justice Department said that the President had made a “protective assertion” of executive privilege over the documents that would ensure “the President’s ability to make a final decision whether t assert privilege following a full review of these materials.”

Read the DOJ letter below: