Now it's his words vs. the president's. (Notable: No Republican senators who questioned Comey at the Senate Intelligence Committee's hearing accused Comey of lying.)
But the president has. He's twice accused Comey of lying in his testimony to Congress that Trump tried to interfere in the FBI's investigations into ousted national security adviser Michael Flynn.
Comey testified that Trump asked him over dinner in January for a loyalty pledge, then, in a February Oval Office meeting, asked everyone to clear the room before he told Comey this:
Trump responded by accusing Comey of lying. (About what, specifically, the president will not say.)
Actually, the fact that there are no tapes doesn't help the president, either.
Comey is, by most accounts, a reliable witness, and so far he's provided the only tangible piece of evidence in this back-and-forth. The way Comey tells it, Trump had suddenly fired him a few days earlier, then tweeted this:
Comey woke up in the middle of the night and had the epiphany “that there might be corroboration for our conversation.”
That corroboration: Comey took detailed notes about his conversations with the president, he told a small circle of people and he testified under oath earlier this month about all this. (Comey is not a perfect witness: When he was FBI director, Comey did misstate a key fact of Hillary Clinton's email case, which the FBI corrected the next day.)
Finally, a fired and frustrated Comey okayed a friend to leak his notes of his conversations with Trump to the New York Times.
Trump, meanwhile, has given mixed messages about what he told Comey.
His lawyer denied that the president told Comey to drop the FBI's various investigations into Flynn. His lawyer also denied that the president asked Comey for a loyalty pledge. At a June news conference in the Rose Garden, Trump also denied he ever said those things.
But Trump also allowed this: “And there'd be nothing if I did say that, according to everything I read today.”
As I wrote earlier, Trump can't have it both ways: Which is it, Mr. President? Did you talk about Flynn or not?
Trump's bluff may have been called. Shortly after he hinted in a news conference that there may be no tapes, the House Intelligence Committee took him up on that, asking for any White House evidence of Trump's conversations with Comey.
Of course, as the president seemed to insinuate — maybe someone else was secretly recording their conversations.