Carroll Quigley, Tragedy and Hope: A History of the World in our Time

The argument that the two parties should represent opposed ideals and policies, one, perhaps, of the Right and the other of the Left, is a foolish idea acceptable only to doctrinaire and academic thinkers. Instead, the two parties should be almost identical, so that the American people can “throw the rascals out” at any election without leading to any profound or extensive shifts in policy.