IT IS still not publicly known what President Trump and Russian President Vladi­mir Putin discussed on Monday during their two hours of one-on-one conversation in Helsinki. But the White House confirmed Wednesday that they did talk about an issue Mr. Putin later raised at their joint news conference in a way that was inappropriate as well as disturbing. Addressing the indictment of 12 Russian military officers on charges of hacking Democrats’ computers and using the stolen data to influence the 2016 election, Mr. Putin suggested the investigative team of special counsel Robert S. Mueller III could be invited to witness their questioning by Russian authorities — provided that similar access was given to Americans “who have something to do with illegal actions on the territory of Russia.” “I think that’s an incredible offer,” volunteered Mr. Trump.

As it turned out, Mr. Putin was trying to equate the Mueller investigation with a sinister Russian campaign against Bill Browder, an American-born financier who has become a Putin nemesis. After his lawyer, Sergei Magnitsky, was jailed and killed for exposing a massive fraud involving senior Russian officials, Mr. Browder persuaded Congress to pass the 2012 Magnitsky Act, which has led to sanctions against numerous officials in the Putin clique. In an attempt to get the sanctions lifted, the Putin government has tried to portray Mr. Browder as the criminal, repeatedly and unsuccessfully seeking his arrest by Interpol.

The latest gambit, on which the prosecutor general’s office in Moscow elaborated Tuesday, would have Russian investigators attend interviews with a host of alleged Browder associates, including current and former State Department officials, a congressional aide and Michael McFaul, a former U.S. ambassador to Russia. Among other things, the Russians would pursue allegations that Mr. Browder channeled money into Hillary Clinton’s presidential campaign: Mr. Putin cited an amount of $400 million, which the prosecutor’s office later revised to $400,000. Mr. Browder says he never contributed to Ms. Clinton.

That Mr. Trump would endorse this cynical and preposterous proposal might be chalked up to ignorance or confusion — except that Mr. Trump knows all about Mr. Putin’s false claims against Mr. Browder. The same charges were the subject of the June 9, 2016, Trump Tower meeting between Russian lawyer Natalia Veselnitskaya and three senior Trump campaign officials, including Donald Trump Jr. The younger Trump agreed to the meeting, which is reportedly a focus of Mr. Mueller’s investigation, after being promised damaging information on Ms. Clinton. The president later dictated a misleading statement , saying the meeting was about adoptions; Mr. Putin had halted U.S. adoptions of Russian children following the passage of the Magnitsky Act.

Mr. Putin’s airing of the same allegations about Mr. Browder and Ms. Clinton in Helsinki only bolsters the case that Ms. Veselnitskaya was acting on the Kremlin’s behalf when she visited Trump Tower. In turn, Mr. Trump’s rush to embrace Mr. Putin’s disingenuous proposal to question eminent Americans about those claims is in keeping with his alignment with Mr. Putin against Mr. Mueller and the U.S. justice system. It shows he did not misspeak at that news conference: he was, in fact, championing Mr. Putin’s agenda.