President Trump has many enemies, some of his own making or even invention. He rails against the media, which he calls “the enemy of the people. He attacks the FBI and the nation’s intelligence agencies, claiming a “Deep State” conspiracy to topple him and the Constitution.

Yet his biggest enemy, the foe that in the end will bring him down, the adversary whom he cannot control, is Donald J. Trump himself.

It was Trump who decided a year ago to clear everybody else out of the Oval Office so that he could privately pressure Jim Comey to end the investigation of Mike Flynn. It was Trump who later fired Comey as head of the FBI, because he thought Comey’s firing would make the Russia investigation go away.

And how do we know that? Because it was Trump who told us.

The investigation did not go away. Comey’s firing in May of 2017 — “one of the worst mistakes in modern political history,” Steve Bannon would later call it — created bipartisan outrage and forced the appointment of Robert Mueller as special counsel. Instead of stopping, the investigation got bigger.

Now we learn that in June of 2017, barely a month after firing Comey, Trump ordered that Mueller be fired as well. White House Counsel Don McGahn, instructed to carry out the firing, refused the order and was prepared to resign rather than play that role in obstructing justice. Trump then relented.

Trump has dismissed the story of Mueller’s attempted firing in typical fashion: “Fake news, folks. Fake news. A typical New York Times fake story.” The problem is that multiple outlets, including his friends at Fox News, have confirmed the New York Times story through sources of their own.

It’s pretty remarkable. Back in June, Trump had just experienced the disastrous backlash created by firing Comey, including criticism from congressional Republicans — it was still fresh in his mind. Yet something about the Mueller investigation so frightened him that he was willing to provoke a far greater firestorm by firing Mueller as well, and on clearly spurious grounds.

That is not the behavior pattern of someone who has nothing to hide, as Trump proclaims himself to be. It is part of an entirely different pattern.

Very early in his presidency, Trump pressured Attorney General Jeff Sessions not to recuse himself from the Russia investigation, because by doing so Sessions would forfeit the capability to protect Trump. When Sessions recused himself anyway — he had no real choice under the law — an angry Trump tried to humiliate his one-time close ally into resignation.

Trump also pressured his second FBI director, Christopher Wray, to fire Deputy Director Andrew McCabe, an effort that Wray blocked by threatening to resign. Trump has reportedly talked of firing Deputy Attorney General Rod Rosenstein as well, also over the Russia investigation.

Throw in the Comey firing and the attempted Mueller firing, then ask yourself: How does that NOT amount to obstruction of justice?

In recent days, Trump has tried to defend his behavior as merely “fighting back,” and he certainly has every right to do that. But there are legal ways to fight back, and then there are illegal ways. Using his power as president to interfere with an investigation, to try to intimidate and even remove those investigating him, falls clearly into that second category.

And sometime in the not-too-distant future, Trump will have to sit down in front of Mueller and try to explain all of this. Once again, he will be his own worst enemy.