Does public opinion exert much influence on public policy? At least at first glance, the answer would be a resounding “no.” Most voters are inattentive to the details of public policy (see Delli Carpini and Keeter 1996, for the most thorough review), a sad fact known since at least The American Voter (Campbell et al. 1960). If one were to generalize from the typical voter depicted in micro-level studies of public opinion, the macro-level electorate would seem incapable of setting the course of public policy. Moreover, it would be implausible that politicians would anticipate that the electorate could do so. Innovations such as Johnson's Great Society, Reagan's conservative agenda, or Clinton's measured moderation must find their source somewhere other than the demand of public opinion.

But the first glance does not provide the correct perspective, underestimating as it does the concentrated energy of informed opinion. Is it possible that public opinion could be an important engine of public policy in the American democracy? We argue in the affirmative. We know that the public's Policy Mood moves systematically over time (Chapter 6) and is a major factor in national elections (Chapter 7). In its liberal phase, the public elects more Democrats; when conservative, it elects more Republicans. All it takes for a policy response then is for the parties to put their ideologically distinct agendas into law when elected, a matter we test next. But the direct action of elections is not the only spark.