Public opinion matters, both as a central element of democratic theory and as a substantive foundation for political representation. The origins and nature of public opinion have long attracted the attention of social scientists. Yet a number of questions remain; among the more perplexing is whether–and under what conditions–public opinion is stable. The answer depends in large part on whether one looks at aggregations of individual opinions (macro public opinion) or at the individual opinions themselves (micro public opinion). In this essay, we explore the macro/micro divide and offer a framework to determine when opinions are likely to be stable or volatile. This framework reflects both the content of the political environment and the nature of individuals' opinions. Using public opinion dynamics surrounding the Patriot Act as a primary example, we discuss the role of opinion stability in interpreting public opinion and in understanding the normative implications of public preferences.