FOR DECADES, and particularly since President Richard Nixon’s administration, public pressure has led presidents to become steadily more open with citizens about how they conduct business, and more mindful of ethics. Major party candidates have released their tax returns, revealing information about their finances and any potential conflicts of interest. Presidential relatives have avoided high office. The Justice Department has insulated itself from the Oval Office. And, as of the Barack Obama presidency, the White House has released voluminous records on who visited the executive mansion grounds so citizens could know who was meeting with the president and his staff.

Some of these practices flowed from formal rules, others from norms based on the American notion that the president works for the people and that transparency and ethical guidelines are essential checks against abuse of that trust. Though presidents have chafed at the expectations that follow from this principle, none before President Trump has so brazenly attempted to reverse the decades-long trend toward an above-board presidency.

The latest news is that Mr. Trump will not routinely release White House visitor records, as Mr. Obama did. The White House cited “grave national security risks and privacy concerns.” The former is not persuasive, since a national security exception was built into the policy. So Mr. Trump must argue that his right to privacy, or that of the lobbyists coming to see him, outweighs the public’s interest in knowing who is getting an audience. We don’t find that persuasive, either.

Mr. Trump’s decision to claw the White House logs back into the shadows follows several other moves that show contempt for the public. As a candidate, Mr. Trump promised to disclose his tax returns; then postponed the release date; then seemed to decide that he never need keep that promise. His excuse — that the IRS is auditing his recent tax forms — has been thoroughly discredited as a rationale, and provides not even phony cover for refusing to release older returns. Given Mr. Trump’s sprawling, secretive business, and unanswered questions about its ties to Russians, his departure from tradition in this matter is particularly unsettling. Nor has he made as clean a break from his business as taxpayers have a right to expect.

Judging from his public statements, Mr. Trump calculates that there is little to no political price to be paid for flouting norms of ethics and openness. But his dismal poll numbers consistently show that Americans question his honesty. A time may come when he needs to ask the American people to have confidence in him. After undoing the nation’s progress toward transparency, he may find that the reservoir of trust is very shallow.