Who is doing the designating? How so (and on what basis and rationale)? And how is this decision made known? How is authority transferred or conferred?
So, I am going to suggest that even within the context of assuming that all authority comes from God, it is a natural, essential feature of political authority in exercise that there be a public act or condition under which it is recognized, before the ruler can rightly and appropriately demand obedience.
Other than the sheerest direct intervention by miraculous sign, this public event or condition is at the hands of men: it is men, for example, who design and regulate the law of succession from one king to the next. In many cases, it is the oldest son, but in some cultures a group of elders select which son it is. Men can change the rule of succession without a revolution against the existing order. So, it seems to me correct to say that whatever we say about whether God puts the authority into the hands of the body politic as a whole for them to pass on, or not, it must be the case that God normally permits the designation of who shall hold authority as a matter for men to determine. (And this does not imply democracy.)
