Niccolò Machiavelli
Discourses on the First Decade of Titus Livius (Chap. 1.20) (English version)
That the consecutive Reigns of two valiant Princes produce great results: and that well-ordered Commonwealths are assured of a Succession of valiant Rulers by whom their Power and Growth are rapidly extended.

When Rome had driven out her kings, she was freed from those dangers to which, as I have said, she was exposed by the possible succession of a weak or wicked prince. For the chief share in the government then devolved upon the consuls, who took their authority not by inheritance, nor yet by craft or by ambitious violence, but by the free suffrages of their fellow-citizens, and were always men of signal worth; by whose valour and good fortune Rome being constantly aided, was able to reach the height of her greatness in the same number of years as she had lived under her kings. And since we find that two successive reigns of valiant princes, as of Philip of Macedon and his son Alexander, suffice to conquer the world, this ought to be still easier for a commonwealth, which has it in its power to choose, not two excellent rulers only, but an endless number in succession. And in every well ordered commonwealth provision will be made for a succession of this sort.