What does Michael Flynn's resignation mean for Trump?
Michael Flynn lasted just over three weeks as President Trump's National Security Adviser, the shortest tenure in the history of the post.
In a sign of the turmoil - and, frankly, chaos - of the current White House, Flynn acknowledged he had misled the vice president.
He was already held in near contempt by many of the intelligence agencies that were working alongside him.
Mainstream Republicans (and Democrats) are aghast at how the Russians are being given a free pass in Ukraine and Syria.
The actual sin was that Flynn had phoned the Russian ambassador to Washington and discussed the issue of sanctions even before Trump was sworn in.
That was a potential (if obscure) crime. But as so often in Washington, it was lying afterwards that was the fatal blow.
He told Mike Pence that sanctions weren't mentioned in the call to the Ambassador.
His late December phone conversation to the Russian Embassy was intercepted by US agents and transcribed.
The deception was plain to see. Ironically, Flynn was trapped by the very intelligence agencies he knows so well and who provide him with top secret information.
So Trump has lost a National Security Adviser with suspiciously close links to Russia, and the story ends there. Right?
Not at all. The problems - and the questions - may be just beginning.
Did Trump know about the phone call?
Did the president even instruct Flynn to raise the question of sanctions with the Ambassador?
Was Flynn actually compromised by the Russians?
Do the Kremlin and its security services have something on Trump himself? (A startling question I put to the President-elect a month ago - he denied it.)
No one knows where this leads. But the relationship between the White House and the Russians has taken an extraordinary twist.
The president has abandoned a loyal ally and one of his earliest supporters in an effort at damage limitation. It may work.
But, equally, his opponents now sense weakness and smell blood.
In any case, the attacks on Flynn were always a route to the real target: the president himself.