OUR SCUT FARKAS:

It now looks like the most consequential Tweet of his presidency to date came a few days after he fired James Comey as FBI director. At 8:26 a.m. on Friday, May 12, Trump wrote: "James Comey better hope that there are no "tapes" of our conversations before he starts leaking to the press!"

That tweet, Comey told the Senate, prompted the now-private citizen to instruct a friend, Columbia Law professor Daniel Richman, to share with the New York Times the contents of contemporaneous memos he had written describing his interactions with the president. The article, published a week to the day Comey was fired, revealed that the president had asked the FBI director to end the criminal investigation into former national security adviser Michael Flynn.

Why did Comey have Richman call the Times? Because, he told the Senate, he hoped that the disclosure of the memo would prompt the appointment of a special counsel to investigate Russia's involvement in the 2016 election and possible collusion with associates of the president's campaign. That is exactly what happened May 17, the day after the Times piece, when Deputy Attorney General Rod Rosenstein named as counsel former FBI director Robert Mueller.

And though Comey would not say if he believed President Trump obstructed justice by urging him to "let go" the investigation into Flynn, he did say he was sure that Mueller would investigate whether obstruction of justice had occurred.

Obstruction of justice, of course, being something past congresses have considered a "high crime and misdemeanor" worthy of presidential impeachment.

In other words: By firing Comey and then tweeting recklessly about it, Trump elevated a long-running but manageable problem--the so-called "Russia thing"--into an independent investigation that seriously endangers his presidency.

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