Bill Priestap is the FBI Director of Counterintelligence.

Bill Priestap was the immediate supervisor of FBI Counterintelligence Deputy Peter Strzok . Priestap is #1, Strzok was #2.

The investigation into candidate Donald Trump was a counterintelligence operation. That operation began in July 2016. Bill Priestap would have been in charge of that, along with all other, FBI counterintelligence operations.

FBI Deputy Peter Strzok was specifically in charge of the Trump counterintel op. However, Strzok would be reporting to Bill Priestap on every detail and couldn't (according to structure anyway) make a move without Priestap approval.

https:// www.zerohedge.com/news/2018-01-26/wsj-asks-what-are-adam-schiff-justice-department-fbi-trying-hide