Comey worked for Sessions, not the other way around. It was up to Sessions to determine if Comey's investigation had merit before recusing himself.
He doesn't get to be the one to determine if an investigation into himself "has merit". It's why we don't ask a police officer to investigate himself regarding charges of police brutality and to get to back to us with the results. We as a society do not ask persons in positions of authority to investigate themselves and determine whether accusations have merit.
The Deep State has created fake constitutional crises every step of the way for the last three and one-half years, regardless. As the AG, you do what's right, and you don't act out of fear of some bogus constitutional crisis.
You can't win that way.
You can't win by collapsing the government. The Deep State has created fake constitutional crises every step of the way and President Trump and people like Sessions have avoided traps set to topple the government every step of the way. Sessions was chosen for AG for his record and the Deep State needed to rip that away by portraying him, and the president who appointed him as lawless.
