President Trump is besieged by problems, including a hostile media and a Democratic Party digging in for total obstruction. But as the FBI investigation of his administration and campaign gathers pace, it is impossible to ignore the fact that the president's biggest problems now, especially involving the investigation, are of his own making.

He refuses and is perhaps incapable of dialing down his combativeness when it is appropriate, and he refuses to do things by the book when it's necessary.

Trump did very well never giving an inch in the election campaign. He never apologized, never backed down. Voters saw this as strength and lined up behind him. Smashing norms and disregarding the Washington swamp's experts were central to his appeal. At times, it has served him well in office, too, but on the whole, it has not.

Had Trump not fired James Comey, he might be mostly in the clear right now. Washington Examiner columnist Byron York made the case that absent that firing, "the political radioactivity of the issue would be ticking down, not up." This is surely true.

Every day, it seems less likely that the supposed underlying offense, Trump's collusion with Russia in meddling in the 2016 election, ever occurred. If it were a real possibility, Comey wouldn't have privately confirmed, up until a few weeks before he was fired, that Trump was not under investigation. After all the leaks from this investigation, nobody has yet let trickle out a scrap of evidence of what that "collusion" might look like.

So the investigation has, as always, instead turned toward the way it is handled or covered up. Why did Trump spend so much time leaning on top officials, including Comey, Director of National Intelligence Dan Coats, and Adm. Mike Rogers, director of the National Security Agency, to back off Mike Flynn, Trump's former national security adviser, who is now under investigation?

There are plausible innocent motivations, but there are no good explanations at this point. Perhaps Trump just disliked the idea that Flynn, a friend and a "good guy," would be treated unfairly. Perhaps the president concluded Comey was an unhinged prosecutor who concealed exculpatory evidence from the public amid a welter of inculpatory leaks and needed to be removed.

These explanations could account for Trump's actions without reflecting ill intent or the cover-up of malfeasance. But these explanations don't excuse bad judgment behind the actions.

A more measured president who properly respected the norms and constraints of his office wouldn't have tried to intervene on Flynn's behalf and would have either kept Comey in place or built a real case (beyond an ambiguous letter from Rod Rosenstein) for firing him.

So now Trump, who hasn't been shown to have done anything wrong regarding Russia, is under widening investigation. On Twitter on Friday, he appeared to blame Rod Rosenstein. He'd be more correct if he blamed himself.