Thanks to a link from Russell Whitaker, I found an essay entitled A Thousand Dusty Codicils by George Monbiot, which contains the following sentences:
Only the people will hold the government to account. They have two means of doing so. The first is to throw it out of office at the next election. This works only when we are permitted to choose an alternative set of policies. But in almost every nation, a new contract has now been struck between the main political parties: they have chosen to agree on almost all significant areas of policy. This leaves the people disenfranchised: they can vote out the monkeys but not the organ grinder. So voting is now a less important democratic instrument than the second means: the ability to register our discontent during a government's term in office.
Monbiot does not take the next logical step: to conclude that voting for or against any of the monkeys is futile as long as the same old organ grinder is playing the tune. Most folks think that voting in every election is the limit of their civic responsibilities, and are aghast if you say that you are opposed to voting on principle. Yet they voice little dissent during any given monkey's term of office, and show no recognition that the same old organ grinder is still in charge (in fact, they usually think that their monkeys are far superior to those monkeys from the other party, whom they demonize relentlessly).
Sadly, it's not easy to see how we can rid ourselves of the organ grinder (whose organs, it seems to me, are the organs of state power). But one helpful step would be to strengthen the fiber of civil society, rather than to focus so incessantly on the doings of the monkeys in various positions of government power. As the bumper sticker says: "Don't vote: it only encourages them."