Epstein and Martin on Public Opinion and the Supreme Court

Does Public Opinion Influence the Supreme Court? Possibly Yes (But We’re Not Sure Why) has just been posted by Lee Epstein, University of Southern California, and Andrew D. Martin, Washington University, St. Louis.  It appears in the University of Pennsylvania Journal of Constitutional Law, Vol. 13, No. 263, 2010.  The article uses quantitative analysis to test the argument made by Barry Friedman and others that public opinion influences the Supreme Court.  While they find an association between the Court and public opinion, importantly they stress that the association does not prove causality, for "it is equally plausible...that the Justices are simply 'social beings confronted with the plethora of stimuli emanating from American culture, media and politics.' In other words, the same things that influence public opinion may influence the Justices, who are, after all, members of the public too."  Other political science work on public opinion shows that public opinion does not naturally flow up from the public, but is mediated especially by elite discourse and partisan politics.  Taking the causality question seriously should require scholars of the Court take seriously work on what public opinion is, and what forms it in the first place.

Here's Epstein & Martin's abstract:

Using qualitative data and historical methods, Barry Friedman asserts with confidence that “we the people” influence the decisions of the U.S. Supreme Court. Using quantitative data and statistical methods, political scientists are not so sure. Despite their best efforts to validate basic claims about the effect of public opinion on the Court, the evidence remains mixed at best.

We enter this dialogue but in a voice distinct from existing political science work. Rather than explore the relationship between the public and the Court on a term-by-term basis, we analyze it at the level of the case. This allows us to exploit more nuanced public opinion data, as well as to attend to the many other case-level factors that may influence the Court’s decisions.

Based on our analysis, we are prepared to say that Professor Friedman is on to something. When the “mood of the public” is liberal (conservative), the Court is significantly more likely to issue liberal (conservative) decisions. But why is anyone’s guess. Professor Friedman posits that the Justices will bend to the will of the people because the Court requires public support to remain an efficacious branch of government. Our analysis could be read to support this view, but it is equally consistent with another mechanism: that “the people” include the Justices. On this account, the Justices do not respond to public opinion directly, but rather respond to the same events or forces that affect the opinion of other members of the public.

Our study proceeds as follows. In Part II, we briefly review the extant literature, emphasizing the similar methodology it invokes but the varying conclusions it reaches. Parts III and IV describe our methods and findings. We end, in Part V, with the implications of our statistical work for Professor Friedman’s claims, as well as for future research assessing the Court’s response to public opinion.