Yes, Zarek is the rightful President in the event that roslyn dies or resigns. He is also basically guilty of corruption of some kind ( or Adam’s bluff wouldn’t have worked) and he is working to incite a mutiny aboard the Galactica…not someone I want as president so I’m kind of okay with Adam doing something to keep him from taking power…
Not to mention that Roslyn is still alive and has not been declared unfit for the job.