Priebus, McMaster, Pence, and possibly some others in the House or Senate are working together to speed along Trump's removal. Priebus can go on to be Pence's Chief of Staff. McMaster is on active duty and not necessarily there by choice. We've heard very little from him since his awkward defense of Trump's shady meeting with the Russians in the Oval Office.

All of the others, like Bannon, Spicer, Conway, etc, know they will be unemployable when Trump is removed. So I doubt it's any of them.

https://twitter.com/jlsinc/status/884817945909743620