What did Donald Trump do today?

He tried to disappear his self-incriminating statement from last year about the Russia investigation.

Trump's morning tweet-period lasted about two hours today, and included this statement: "Not that it matters but I never fired James Comey because of Russia! The Corrupt Mainstream Media loves to keep pushing that narrative, but they know it is not true!" 

Even by Trump standards, this is a breathtaking lie. 

On May 9 of last year, Trump fired FBI Director James Comey, with the explanation that he had done so because Comey was unfair to Hillary Clinton. (Trump has publicly demanded that his own Justice Department find some way to investigate Clinton.) 

On May 10, in an Oval Office meeting, Trump said this to Russian foreign minister Sergey Lavrov and Russian Ambassador Sergey Kislyak: “I just fired the head of the F.B.I... I faced great pressure because of Russia. That’s taken off.” 

On May 11, Trump sat for an interview with NBC's Lester Holt. Asked about the firing, Trump said he had intended to fire Comey no matter what, adding, "When I decided [to fire Comey], I said to myself, I said, 'You know, this Russia thing with Trump and Russia is a made up story.'" 

As recently as this month, Trump's own lawyer, Rudy Giuliani, said that Trump fired Comey because "Comey would not, among other things, say that he wasn’t a target of the [Russia] investigation. He’s entitled to that. Hillary Clinton got that and he couldn’t get that. So he fired him and he said, 'I’m free of this guy.'" (In reality, nobody is "entitled" to be told they're not a target of a criminal investigation--especially if they are or are likely to become one.)

The reason that it does matter is that by admitting that Comey's firing part of an effort to end the Russia investigation, Trump was demonstrating "corrupt intent," which is an element of the crime of obstruction of justice. 

Trump's sudden interest in recanting his confession probably has to do with the revelation that he sought to make Russia part of the "recommendation" that Trump commissioned from Rod Rosenstein, which he then used to justify Comey's firing. Rosenstein did not comply, but he did announce the appointment of a special counsel to take over the Russia investigation on May 17.

Why is this a bad thing?

• For a president to lie this baldly isn't just insulting, it's damaging to the office.

• You can't un-incriminate yourself by pretending you didn't say the things that incriminated you.