Seriously, folks. This isn't good.

Yesterday, President Trump issued a one-word tweet, all caps: "OBAMAGATE!"

Nobody is quite sure exactly what this nebulous but doubtless (eye-roll) very evil conspiracy entails. But in general terms, it seems to be a plot by President Obama and Vice-President Biden and various other of Mr. Trump's favorite "villains" to undermine his presidency before it even began. It seems to have continued ever since, aided and abetted by a secret government-within-the-government called the "Deep State," which uses the intelligence community and even his own Department of Justice against him. Nobody is exactly sure about the details, and neither Mr. Trump nor his supporters seem able to precisely define "Obamagate," but plenty of people on the far right believe implicitly that it's a thing.

This imaginary plot seems to occupy more and more of Mr. Trump's mind these days. Today, he tweeted the following:

Like many on the right, Sen. Graham may have lost his independence and his once-formidable integrity seems to be AWOL, but he has not lost his mind. He diplomatically declined the president's suggestion, politely explaining that he thought it was a bad time to do that. One more example of a phenomenon White House staffers described to the Mueller investigation (part of Obamagate, I think, though I might be wrong): others stepping in to save Mr. Trump from destroying himself. Can you imagine what would happen if such hearings were actually held?

It's hard to believe that we have come to such a pass in this country that the President of the United States can rave incoherently about his predecessor organizing imaginary criminal plots against him and we simply take it in stride. But then, this is a president who has consistently behaved ever since he took office as if disagreement with him or opposition to him were inherently illegitimate.

This is not a healthy man, folks. I make no psychiatric diagnosis; I'm not qualified to do that, and it would be unethical to do so even if I were. But as I've said before, I think it's perfectly legitimate for even laypeople to ask, "Is this the way a normal person behaves?"

Nor is having a Chief Executive who sees dissent as inherently illegitimate a healthy thing for a free people. Having one who thinks based on no particular evidence that his predecessor is the kingpin of a criminal conspiracy plotting against him isn't exactly reassuring, either. And anyone who doubts the damage Mr. Trump has done to America's political culture has only to reflect on the number of people who, again based on no particular evidence, agree with him.

ADDENDUM: Oh. And the following have been fact-checked. More than once.

The President of the United States to the contrary, Barack Obama and Hillary Clinton were not co-founders of ISIS.

And no. Ted Cruz's father did not conspire with Lee Harvey Oswald to assassinate President Kennedy.

Just in case you wondered. And yes, Mr. Trump did, indeed, float both theories.

ADDENDUM II: Another one-word "OBAMAGATE!" tweet today.

Obsessive much?