Nicholas Georgakopoulos is the Harold R. Woodard Professor of Law, Indiana University Robert H. McKinney School of Law, Indianapolis. Frank Sullivan, Jr., is the Indiana University Bicentennial Professor at the same institution and was an Associate Justice of the Indiana Supreme Court from 1993 until 2012.

Can we see how different the 5–4 majorities of the United States Supreme Court are? What is the number of swing votes connecting them and their relative importance?

In a previous article in this journal, we developed a method for displaying the swing votes of a supreme court, the (tight) majorities they connect, and the opinions those majorities issue. We apply our method to compositions of the United States Supreme Court after 1946 that have over 50 tightly split opinions: the compositions of the court defined by its junior justice being Vinson, Stewart, Powell, Stevens, O’Connor, Kennedy, Breyer, Alito, and Kagan.

This look at 5–4 coalitions and swing votes primarily reveals an ebb and flow of a tide of a judicial practice we call fluidity, which corresponds to the flexibility or variability with which justices of a supreme court form tight coalitions. The graphs allow us to observe the number of coalitions, their opinions, and swing votes. Fluidity reaches its high point during the composition defined by Stevens as the junior justice, i.e. from 1975 to 1981. Its adjacent compositions, Powell’s (1972–75) and O’Connor’s (1981–86), are similar. However, the recent compositions, defined by the junior justices being Alito (2006–09) and Kagan (2010–16), differ. Those appear similar to the early ones, defined by Vinson (1946–49) and Stewart (1958–62). Whereas we focus on the graphical representation of 5–4 coalitions and swing votes, several additional phenomena follow the same pattern.

The graphs of the compositions that exhibit high fluidity are different in having more coalitions (9 to 11), linked by more swing votes (in the teens), with those coalitions being closer to proportional in the number of opinions that they issue. The graphs of the coalitions with low fluidity display few coalitions (3 or 4), few swing votes (2 or 3), and even fewer, usually two, coalitions doing the lion’s share of issuing opinions. Additionally, the index of fluidity follows that pattern, reaching 0.57 for the most fluid composition of Stevens but being around 0.30 for the least fluid ones. The issuance of opinions with a political slant opposite to the majority of opinions of that coalition, what we call contraslantedopinions, again has a high during the fluid compositions (from 2.5 percent to 5 percent compared to 0 percent to 2 percent in the less fluid ones). We speculate about the causes of this phenomenon: how it might relate to the composition of the court by the justices’ appointing party but fails to do so.

Secondarily, this analysis reveals the limitations of attempts to fit supreme court adjudication in locational models, especially the median voter theorem. The strongest discrepancies with the median voter theorem are that (1) often the most active swing vote is not the justice who according to the ideological rankings is the median; (2) justices far from the median can be the second most active swing vote; and (3) the busiest swing vote changes without a change of the median justice. Moreover, even a multi-dimensional locational model cannot remain accurate because adjudication makes new factors become important, what from the perspective of locational models would correspond to the creation of new dimensions. We offer the Apprendi line of cases and the uniqueness of its coalition as an example of a creation of a new dimension that could not have been anticipated.

For the related literature, we refer to our prior article.

Our approach stands in contrast to attempts to identify a single justice as the swing vote to the extent that we reveal all the swing votes of each court. Notably, our approach reveals Scalia and Thomas to be significant swing votes despite not being in the ideological middle of the court.  [Read entire Article here].