Trump sets out to deceive people. As he has put it, “I play to people’s fantasies.”

Caveat emptor: When Donald Trump says something happened, it should not change anyone’s estimation of whether the event actually happened. Maybe it did, maybe it didn’t. His claim doesn’t change the odds.

Which brings us to Russia.

Russia’s interference in the 2016 presidential campaign was an attack on the United States. It’s the kind of national-security matter that a president and members of Congress swear to treat with utmost seriousness when they take the oath of office. Yet now it has become the subject of an escalating series of lies by the president and the people who work for him.

As Comey was acknowledging on Monday that the F.B.I. was investigating possible collusion between Russia and the Trump campaign, Trump was lying about it. From both his personal Twitter account and the White House account, he told untruths.

A few hours later, his press secretary, Sean Spicer, went before the cameras and lied about the closeness between Trump and various aides who have documented Russian ties. Do you remember Paul Manafort, the chairman of Trump’s campaign, who ran the crucial delegate-counting operation? Spicer said Manafort had a “very limited role” in said campaign.