What did Donald Trump do today?

He pretty much declared the DOJ his personal police force.

Just before 2 A.M. this morning, Trump was up rage-tweeting about the news that federal prosecutors, following sentencing guidelines, were recommending a prison sentence of seven to nine years for his political ally Roger Stone. 

Trump has good reason to be concerned: Stone could do enormous damage if he decided to start cooperating with prosecutors. (If Trump pardoned Stone, then Stone would lose his Fifth Amendment privilege against self-incrimination and could be forced to testify against Trump.) Stone was convicted last year of lying to Congress and threatening a witness in his attempt to shield Trump from the Mueller investigation.

That tweet took on enormous significance as the day wore on. The sequence of events has gone as follows:

Around noon, the DOJ announced that it was planning on making the recommended sentence much more lenient. It is extremely rare for federal prosecutors to depart from those guidelines, unless the convicted person has helped with other investigations.

Then, over the course of the afternoon, every single one of the four prosecutors who made the original recommendation quit the case, and one resigned from the DOJ entirely, apparently in protest.

Then, Trump abruptly withdrew his nomination of Jessie Liu to join the Treasury Department. Liu was the U.S. Attorney who oversaw the Stone case. She was scheduled to appear at a Senate confirmation hearing for the new position, where she would undoubtedly have been forced to talk about Trump's actions today.

Trump himself insisted that he hadn't done anything to cause the change—but that he would have been legally justified in doing so. (Trump has used this formulation—I didn't do it but I could have—on everything from the Ukraine scandal to conspiring with the Russian government on the 2016 election.)

This evening, NBC reported that Trump's hand-picked Attorney General, William Barr, has assumed personal control over all Justice Department matters that affect Trump personally, including the Stone sentencing. A skeleton crew of new prosecutors have already submitted a new, much more lenient sentencing recommendation today. In the past week, Barr has also made himself the final authority on approving investigations into election tampering, and set up a special reporting conduit for anything Trump's personal lawyer Rudy Giuliani wants to have "investigated."

Stone is one of a number of Trump supporters who are now in prison or awaiting sentencing, including his campaign chairs Paul Manafort and Rick Gates. Trump is tweeting about them tonight.

Why does this matter?

• You either have a fair and independent justice system, or one that tolerates crime when it benefits the president.

• The president is not above the law.

• It's bad if a president's actions force public servants to choose between his demands and their consciences.