Public deliberation and debate are central to both our normative conceptions and everyday observations about liberal democracies. Politicians, journalists, scholars, and ordinary citizens in the United States often refer to the public debate about health care, or gay marriage, or Iraq, or some other issue of national importance. Concerned individuals also often call for a public debate about a topic that has either been ignored or considered unproblematic. In some cases, they might have a specific setting in mind: the floor of the Senate, a town meeting, or perhaps a radio talk show. But in general, what people mean by a public debate, I suspect, is something like a national discussion extending beyond any particular institution or building. Public debates, in this intuitive definition, involve political elites discussing and contesting basic issues, the media reporting these fights and taking sides, and the general public coming to regard the topic of debate as an important national issue.

This book builds on this intuition by analyzing what public debates are, whom they involve, and why they matter. My central claims are that public debates produce new ideas, shift the weight of elite opinion, and change the language elites use to discuss certain political issues. For analytical clarity, I conceive of this process as a three-step sequence:

• Step One: Public debates create and consolidate “frames,” which I define as an ordered set of messages concerning some aspect of the political world. These frames influence political behavior and can also become enduring elements of political culture.

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