You have to first get recommendation from the department. In general, if
tenured professors in your field vote for your case, other professors will
just ok it. But it is true that in general you have to get pass from all
tenured professors. I know some people were screwed because of some power
struggles in the department or college. If some tenured professors strongly
disagree, even if he/she is not in your field, you are in trouble. Usually
graduate students have very little such information. B