The nomination of the Donald Trump hyper loyalist Kash Patel to serve as FBI director is unusual.

First, the job is currently occupied, by one Christopher Wray — himself a Trump appointee — who technically has three years left on his 10-year term of service. On Wednesday, however, Wray preemptively capitulated to Trump by committing to resign at the end of Joe Biden’s presidency, saying he wished “to avoid dragging the bureau deeper into the fray,” politically.

Stranger still — and likely unprecedented — is that Patel has sued the man he hopes to replace,...