Political theory is, in short, the study of the theoretical underpinnings of politics. Political theorists attempt to devise theories to explain how political systems actually work. It is distinguished, among political scientists, from the more quantitative side of the discipline, one which focuses on using polls and data to understand political behavior.
Political theory involves the work of philosophers and historians as well as political scientists. This is because a major concern of philosophers over time, from Plato to Confucius to Karl Marx, has been the characteristics of an ideal society. Thomas More, for example, was a philosopher who was also a political theorist, because he sought, in his work Utopia, to lay out a picture of what an ideal society would actually look like. Machiavelli was a political theorist who dispensed with notions of an ideal society and claimed that political decisions should be made based on a realistic appraisal of human nature. Occasionally politicians themselves have been political theorists. For example, James Madison, considered the "father" of the United States Constitution, was instrumental in developing a theory of republican government even as he helped put it into practice.
Modern political theorists study such topics as liberalism and radicalism, comparative government, the relationship between individuals and the state, and the effects of technology on politics.