Officials said Mr. Pence had told others in the White House that he believed Mr. Flynn lied to him by saying he had not discussed the topic of sanctions on a call with the Russian ambassador in late December. Even the mere discussion of policy — and the apparent attempt to assuage the concerns of an American adversary before Mr. Trump took office — represented a remarkable breach of protocol.
The F.B.I. had been examining Mr. Flynn’s phone calls as he came under growing questions about his interactions with Russian officials and his management of the National Security Council. The blackmail risk envisioned by the Justice Department would have stemmed directly from Mr. Flynn’s attempt to cover his tracks with his bosses. The Russians knew what had been said on the call; thus, if they wanted Mr. Flynn to do something, they could have threatened to expose the lie if he refused.