The most enduring political debate in the United States revolves around the size and scope of the federal government and its activities to manage the economy and provide public assistance to individuals who cannot or have not done well in the marketplace. This is the conflict between liberals and conservatives, and it is probably the principle political conflict in all large political societies. On this dimension, liberals advocate greater government control of the economy, more public ownership of industry, high levels of social welfare benefits (especially to the unemployed, elderly, infirm, etc.), and higher taxes (i.e. a greater public share of private wealth). Conservatives, in contrast, advocate less government control of the economy, a smaller government role in business, private property rights, small social welfare benefits, and lower taxes. You can see this conflict in the debate over issues like health care, taxes, welfare, and the stimulus plan.
Often, when people talk about liberals and conservatives in American politics, they talk about issues that are outside of this size and scope of government dimension, like abortion, gay rights, and the death penalty. These issues are important, but they are not (yet) a really enduring part of the liberal-conservative conflict. Political scientists sometimes call these kind of issues "second dimension" issues. These types of issues--which don't focus on the role of government in the economy and the relationship between private property and public welfare--come and go as society evolves and our moral and cultural concerns evolve. In the past, second dimension issues have included slavery, prohibition, suffrage, and desegregation. Though these issues are disparate, they tend to revolve around governments role in structuring social society, as opposed to our economic society.
Sometimes, first dimension liberals are on the side of government intervention in private morality (as in the case of antidiscrimination laws) and sometimes it is first dimension conservatives who support state control of morality (as in the case of abortion or drugs). Because of this inconsistency, political scientists are often hesistant to group moral or social issues into the same category as economic issues since there is no hard and fast rule about which side is "liberal" and which is "conservative" when it comes to government control of individual morality.
