NYT:

President Trump on Wednesday invoked executive privilege to block Congress from obtaining documents about how a citizenship question was added to the 2020 census, ahead of a House committee vote to recommend that two cabinet secretaries be held in contempt of Congress over the matter.
In a letter to the chairman of the House Oversight and Reform Committee, Representative Elijah E. Cummings of Maryland, the Justice Department said that Mr. Trump had decided to invoke his secrecy powers because Mr. Cummings had “chosen to go forward with an unnecessary and premature contempt vote.” The letter came just as Mr. Cummings was convening the panel to consider a contempt recommendation for Attorney General William P. Barr and Commerce Secretary Wilbur Ross.
While Mr. Cummings put off the vote for several hours to allow lawmakers to review Mr. Trump’s privilege assertion, he made it clear that he did not intend to back down, escalating the latest battle between the House and the president over the Constitution’s separation of powers.

No wonder they are continuing to fight: The materials could well reveal that Secretary Ross and others lied to Congress.