While Aristotle indicates preference for monarchy or aristocracy in which philosopher king/s govern, he thinks that such a regime either will not arise or will be corrupted if it is established. His turn to 'polity' is predicated on assumption that it is achievable and will be stable. Mixture of aristocratic & democratic principles will provide 'checks and balances.'
Aristotle's theory revolves around conflict pitting 'greed and paranoia' of rich against 'hunger and envy' of poor. He assumes that all societies are permanently divided into competing classes. Key is to contain and moderate strife via constitution incorporating institutions *representative* of major 'factions' (Madison's term in *Federalist #10): crown, council, assembly. Thus, A posits basic principles of representative government and, in doing so, conveys fundamentally elitist character of such rule.
Too bad for those who are too poor, too scattered, too unorganized, too weak (in Aristotle's time, women and slaves because he thought they were 'naturally' deficient in reason) because representative government is for those capable of and "interested" in being represented. Michael Hoover