The inclusion of fraudulent Steele allegations in the Obama admin ICA, together with the immediate felony leak, was critical step in destabilizing and almost toppling Trump admin. Events partly covered in both SSCI and Horowitz from different perspective.
in early Dec 2016, WaPo archive.is/WHMke said CIA told congressional leaders that, according to their "secret assessment", "Russia intervened in the 2016 election to help Donald Trump win the presidency". Also, a core assertion of Steele dossier and Hillary campaign. 
3/ as of now, that is received wisdom of US media, but it was an important extension of Russiagate narrative at the time and the basis for the extension at that time remains unclear.
4/ WaPo reported "a second senior U.S. official" said they had "identified individuals [who] pass[ed] the Democratic emails to WikiLeaks", but "those actors were “one step” removed from Russian government, rather than government employees".
Who?
Still not publicly identified.
Who?
Still not publicly identified.
5/ Concurrently, incipient Democrat resistance was pressuring Obama admin to "declassify more information about Russia's alleged interference in the U.S. election" e.g. Steele stenographer David Corn's article in Politico on Nov 30 politico.com/story/2016/11/…
6/ On Dec 9, WaPo also reported that Obama admin had announced a "full review" of Russia hacking to be available as a housewarming present for incoming Trump administration.
7/ despite the importance of the report, Obama admin, whose final act was memo to file saying that everything had been "done by the book", provided no formal written terms of reference for the full review. SSCI reported that instructions were given orally at NSC meeting on Dec 6.
8/ the oral instructions were apparently that report "include everything the IC knew about Russian interference in the 2016 elections", as well as "historical context" of prior interference and recommendations.
9/ Clapper immediately met with Julia Gurganus, National Intelligence Officer (NIO) for Russia and Eurasia, and Vinh Nguyen, NIO for Cyber Issues, to discuss tasking, scope and responsibilities.
10/ proceed to for continuation
