(CNN) President Donald Trump is deeply invested in the idea that there is a "Deep State" embedded within the government bureaucracy -- and centered in the Department of Justice -- which actively worked to defeat him in 2016 and then sought to undermine him once he won the presidency.

That conspiracy theory, which has never had much merit, suffered a near-fatal blow Friday afternoon when the Department of Justice declined to pursue criminal charges against former FBI deputy director Andrew McCabe. (McCabe is a CNN contributor.)

That decision ends a nearly-two-year investigation into whether McCabe, in his role as a senior official in the FBI, lied to investigators about conversations he had with reporters. McCabe had long insisted that if he had done so it had been purely accidental, and noted that, in his role, he was authorized to speak to the media.

Trump spent much of the investigation dumping on McCabe, a man who he insisted was, along with former FBI director James Comey, at the center of the "Deep State" conspiracy against him.

On the day McCabe was fired -- less than two days before his planned retirement from the bureau -- Trump tweeted this

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