The US “two party system” is a ratchet mechanism. A ratchet consists of a base, a gear, and a pawl. The base is the electoral system: “flawed” but unchangeable; “the best we have”. The gear is the Republican Party: its rotation broadly marks imperial progress. The pawl is the Democratic Party: it allows the gear to rotate freely while arresting counter rotation.

While there is friction between the parts, they are not opposed. They all work together to produce a common end more efficiently than they could in isolation.