everyone is focusing on who leaked the existence of the Flynn-Kislyak call to Ignatius of WaPo. But there was a second and even more important phase of anti-Flynn leaking on or just before Feb 9, 2017.

2/ initial leak to Ignatius only disclosed existence of call, which was then levered into antagonistic questioning of Pence, who unwisely responded. 2nd phase of leaking disclosed contents of call, including supposed detail that Flynn had discussed sanctions, contradicting Pence

3/ leaks broken in story by Miller, Entous and Nakashima in WaPo https://www.washingtonpost.com/world/national-security/national-security-adviser-flynn-discussed-sanctions-with-russian-ambassador-despite-denials-officials-say/2017/02/09/f85b29d6-ee11-11e6-b4ff-ac2cf509efe5_story.html archive http://archive.is/5hOg7 

4/ their headline was that officials had discussed content of Flynn's calls. They went far beyond merely disclosing existence.

5/ WaPo said that NINE "current and former officials" in "sernior positions at time of calls" spoke about the classified information. So some of the leaking officials were in subgroup of officials departed between Dec 29 and Feb 9.

6/ this article also appears to initiate the conflation of expulsion of diplomats and Executive Order 13757 sanctions against Russian intel agencies and intel officials, that had previously been distinguished as separate measures.

7/ while the nine "current and former" officials said that Flynn talked about "sanctions" it seems implausible that ,they discussed Executive Order 13757 sanctions, but not implausible that there was brief discussion of expulsions

8/ the best evidence of this point are the notes and 302 of interview, where Strzok raised issue of expulsions, but there are NO notes or 302 mention of sanctions (under Executive Order 13757). I.e. the NINE officials not only leaked information, they leaked false information.