To oversimplify: Democrats are for Big Government; Republicans are against it.
To oversimplify somewhat less, Democrats aren't always for Big Government, and Republicans aren't always against it. Democrats treasure civil liberties, whereas Republicans are more tolerant of government censorship to protect children from pornography, or of wiretapping to catch a criminal, or of torture in the war against terrorism. War in general and Iraq in particular--certainly Big Government exercises--are projects Republicans tend to be more enthusiastic about. Likewise the criminal process: Republicans tend to want to make more things illegal and to send more people to jail for longer. Republicans also consider themselves more concerned about the moral tone of the country, and they are more disposed toward using the government in trying to improve it. In particular, Republicans think religion needs more help from society, through the government, while Democrats are touchier about the separation of church and state.
Many people feel that neither party offers a coherent set of principles that they can agree with. For them, the choice is whether you believe in Big Government or you don't. And if you don't, you call yourself a libertarian. Libertarians are against government in all its manifestations. Domestically, they are against social-welfare programs. They favor self-reliance (as they see it) over Big Government spending. Internationally, they are isolationists. Like George Washington, they loathe "foreign entanglements," and they think the rest of the world can go to hell without America's help. They don't care--or at least they don't think the government should care--about what people are reading, thinking, drinking, smoking or doing in bed. And what is the opposite of libertarianism? Libertarians would say fascism. But in the American political context, it is something infinitely milder that calls itself communitarianism. The term is not as familiar, and communitarians are far less organized as a movement than libertarians, ironically enough. But in general communitarians emphasize society rather than the individual and believe that group responsibilities (to family, community, nation, the globe) should trump individual rights.
The relationship of these two ways of thinking to the two established parties is peculiar. Republicans are far more likely to identify themselves as libertarians and to vilify the government in the abstract. And yet Republicans have a clearer vision of what constitutes a good society and a well-run planet and are quicker to try to impose this vision on the rest of us. Now that the Republican Party is in trouble, critics are advising it to free itself of the religious right on issues like abortion and gay rights. That is, the party should become less communitarian and more libertarian. With Democrats, it's the other way around.
Very few Democrats self-identify as libertarians, but they are in fact much more likely to have a live-and-let-live attitude toward the lesbian couple next door or the Islamofascist dictator halfway around the world. And every time the Democrats lose an election, critics scold that they must put less emphasis on the sterile rights of individuals and more emphasis on responsibilities to society. That is, they should become less libertarian and more communitarian. Usually this boils down to advocating mandatory so-called voluntary national service by people younger than whoever is doing the advocating.
Libertarians and communitarians (to continue this unjustified generalizing) are different character types. Communitarians tend to be bossy, boring and self-important, if they're not being oversweetened and touchy-feely. Libertarians, by contrast, are not the selfish monsters you might expect. They are earnest and impractical--eager to corner you with their plan for using old refrigerators to reverse global warming or solving the traffic mess by privatizing stoplights. And if you disagree, they're fine with that. It's a free country.
The chance of the two political parties realigning so conveniently is slim. But the party that does well in the future will be the one that makes the better guess about where to place its bets. My money's on the libertarians. People were shocked a couple of weeks ago when Ron Paul--one of those mysterious Republicans who seem to be running for President because everyone needs a hobby--raised $5 million from July through September, mostly on the Internet. Paul is a libertarian. In fact, he was the Libertarian Party presidential candidate in 1988. The computer revolution has bred a generation of smart loners, many of them rich and some of them complacently Darwinian, convinced that they don't need society--nor should anyone else. They are going to be an increasingly powerful force in politics.