@pjw for the first exception: Weaponising this during the election cycle. The person will not have access enough to deal with concerns of voters which does give an unfair disadvantage,
second exception: at least in my country there are exceptions, when you can hold an office, and I think of things like mass-polluting the environment, war crimes or infrastructure hazards against communities. This does not make someone fit DURING the sentence to be in the office from my perspective.