At a critical juncture in Donald Trump’s presidential campaign last year, his son Donald Trump Jr. met with Natalia Veselnitskaya, a Kremlin-connected Russian lawyer who promised to share political dirt on Hillary Clinton. Paul Manafort, Mr. Trump’s campaign chairman at the time, and Jared Kushner, Mr. Trump’s son-in-law and a key strategist, also attended.

The June 9, 2016, meeting is of obvious interest to Robert Mueller III, the Justice Department special counsel investigating the Trump team’s potential involvement in Russia’s effort to influence the presidential election. In two clumsy statements over the weekend, the younger Mr. Trump on Saturday said the meeting was related to Russia’s freezing of an adoption program popular with Americans. When confronted a day later with a Times story citing authoritative sources that Ms. Veselnitskaya had promised damaging material on Mrs. Clinton, he said that the information she supplied was essentially meaningless and merely a “pretext” for discussing the adoption issue.

On the face of it, this seemed a clear though perhaps unintended admission by Donald Trump Jr. that he had gone into the meeting expecting damaging information, and the episode is clearly grist for Mr. Mueller’s mill. As is a report Monday night by The Times that the president’s son had received an email saying Ms. Veselnitskaya’s information came from Moscow. But his shifty statements are also further evidence of how freely his father and the people around the president contort the truth. Only six months in, President Trump has compiled a record of dishonesty — ranging from casual misstatements to flat-out lies — without precedent in the modern presidency. Equally disheartening is his team’s willingness to share in his mendacity.