No Difference Between the Major Parties

I think the following quote from Carroll Quigley's book, Tragedy & Hope: A History of the World in Our Time, says it all:

The chief problem of American political life for a long time has been how to make the two Congressional parties more national and more international. 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. The policies that are vital and necessary for America are no longer subjects of significant disagreement, but are disputable only in terms of procedure, priority and method. ... Either party in office becomes in time corrupt, tired, unenterprising, and vigorless. Then it should be possible to replace it, every four years if necessary, by the other party, which will be none of these things but will still persue, with new vigor, approximately the same basic policies.