One of the greatest political mysteries of our time is why President Trump has clung — and continues to cling — so steadfastly to the perfidious Michael Flynn.

Flynn, the president’s former national security adviser, is at the nexus of Trump’s problems. There was Flynn’s lobbying on behalf of Turkey and his contacts with Russia. There was Trump’s dismissal of all warnings to steer clear of Flynn; his refusal to fire Flynn as soon as he was alerted to the fact that Flynn posed a security risk; his efforts to impede or even terminate the investigations of Flynn.

Not only has Trump staunchly defended Flynn — even after firing him — he is apparently still in contact with him, sending him encouraging messages. As Michael Isikoff reported last week for Yahoo News about a dinner Flynn convened with “a small group of loyalists”:

Not only did he remain loyal to President Trump; he indicated that he and the president were still in communication. “I just got a message from the president to stay strong,” Flynn said after the meal was over, according to two sources who are close to Flynn and are familiar with the conversation, which took place on April 25.

This level of extreme fealty is puzzling. It extends beyond basic loyalty to an early supporter. It seems to me that there is something else at play here, something as yet unknown. Trump’s attachment to Flynn strikes me less as an act of fidelity and more as an exercise in fear. What does Flynn know that Trump doesn’t want the world to know?

What are the dirty details of what could only be called The Flynn Affair?

Governor Chris Christie of New Jersey, who served as head of the Trump transition team before being brushed aside for Vice President Mike Pence, said he warned Trump about Flynn. As Christie said earlier this week: “I didn’t think that he was someone who would bring benefit to the president or to the administration, and I made that very clear to candidate Trump, and I made it very clear to President-elect Trump.”