Consider the implications. At the very beginning of Trump’s presidency, as soon as he lied in that press conference, Vladimir Putin and Russian intelligence possessed the ability to unmask Trump as a liar to the American public, revealing damaging information to Congress and the public about which they had previously been ignorant. BuzzFeed’s account of the negotiations involving a potential Trump Tower in Moscow hints at the wealth of documentary evidence that the Russians would possess to back up their claims.

As it would turn out, that was merely the beginning of their leverage. In September 2017, Donald Trump Jr. gave sworn Senate testimony that may be contradicted by Thursday’s revelations, raising the prospect that the Russians have been in possession of evidence suggesting that the president’s son may have committed a felony. And once Cohen lied to Congress about the matter, the Russians were in a position to expose the unlawful behavior of Trump’s personal attorney.

Those particular bits of Russian leverage over Trump are gone now that Robert Mueller’s investigation has revealed the truth to Congress and the public. But there is so much that we still don’t know about the Trump Tower deal, the president’s role in negotiating it, and the reasons his inner circle took extraordinary legal risks to hide the truth about it.

Read: Is WikiLeaks a Russian front?

“The Kremlin knows the answer to these questions,” says Susan Hennessey, a former National Security Agency lawyer, on a Lawfare podcast. “And unless the answers here are the most innocent possible explanations … if it’s anything other than that, the United States is in an incredibly dangerous position, because the United States is in a position where the American president is aware that a hostile foreign adversary potentially has devastating—politically devastating and potentially legally and criminally devastating, if not for him, then for members of his family or organization—that a hostile foreign adversary has that information on him, and those really are the kinds of conditions where your worst nightmare is about blackmail and influence.”

Perhaps the public will ultimately learn why Trump and some of his closest associates lied about business opportunities that they were pursing in Moscow during the 2016 election. But the mere fact that they did lie, for whatever reason, gave a powerful geopolitical adversary at least some leverage over an American president and his son. And Trump knew about the leverage as soon as he lied to the public about Russia, and again when he watched his son and his then attorney lie to Congress, raising the stakes to a matter of clear criminality. Elected officials have resigned in disgrace for less serious transgressions.