U.S. Supreme Court: Lines of Succession and Ideological Alignment


Though there are now only nine seats on the U.S. Supreme Court, the tables below list eleven lines of succession. There is one for the chief justiceship and ten for the associate justiceships that Congress has created at one time and another, as it has changed the size of the Court. In other words, two associate justiceships have “died out” in the course of the Court’s history. The present members of the Court, in addition to the chief justice, hold the first, second, third, fourth, sixth, eighth, ninth, and tenth associate justiceships created by Congress.

The horizontal dimension of the tables list each the eleven seats: the chief justiceship and ten associate justiceships. Justices are listed for each seat in chronological order, beginning with the justices nominated by Washington and ending with the justices nominated by Trump.

There are two horizontal divisions. The first, indicated by a double red line, delineates presidencies. The beginning of every justice’s term is associated with the president who nominated that person to a seat on the Court. The end of each justice’s term is associated with the president who was in office when the justice’s term ended by resignation or death.

The second horizontal division, indicated by alternating bands of gray and white, delineates chief justiceships. Thus the reader can see which justices served with a particular chief justice. The “Roberts Court,” for example, has thus far included Roberts and — in order of ascension to the Court — Stevens, O’Connor, Scalia, Kennedy, Souter, Thomas, Ginsburg, Breyer, Alito, Sotomayor, Kagan, and Gorsuch.

Because there is a separate line of succession for the chief justiceship, persons who were already on the Court and then elevated to the chief justiceship are listed in two different places. Also, the names of a few other justices appear in more than one place because they served non-consecutive terms on the Court.

The table is divided into three parts, for ease of reading. (Zoom in if the type is too small for you.) The first part covers the chief justiceship and associate justice positions 1-3; the second part, associate justice positions 4-7; the third part, associate justice positions 8-10.


The next (very long) graph gives statistics about the frequency with which justices have disagreed with one another in non-unanimous cases, for October Term 2005 through October Term 2017. (The use of non-unanimous cases highlights the degree of disagreement among justices, which would be blurred if all cases were included in the analysis.)

I used the statistics which underlie the preceding graph to construct the following index of defection (D) for each justice, by term:

D = percentage disagreement with members of own wing/percentage disagreement with members of opposite wing.

The wings are the “conservative” wing (Gorsuch, Alito, Thomas, Scalia, Roberts, and Kennedy) and the “liberal” wing (Breyer, Ginsburg, Kagan, Sotomayor, Souter, and Stevens).

The lower the index, the more prone is a justice to vote with the other members of his or her wing; the higher the index, the more prone is a justice to vote with members of the opposing wing. Here’s a graph of the indices, by term:

Kennedy’s long-standing proneness to defect more often than his colleagues grew markedly in the 2014-2015 terms and receded a bit in the 2016 term. His turnaround in the 2017 term restored him to the Court’s “conservative” wing.

Roberts slipped a bit in the 2017 term but is more in step with the “conservative” wing than he had been in the 2014-2015 terms.

Gorsuch started out strongly in his abbreviated 2016 term (he joined the Court in April 2017). His slippage in the 2017 term may have been due to the mix of cases at stake.

Perhaps that’s the reason for Roberts’s slippage in the 2017 term — or perhaps Roberts is “growing in office”, as leftists like to say about apostate conservatives. Time will tell.

What’s most striking about the preceding graphs, other than Kennedy’s marked departure from the “conservative” wing after the 2010 term, is the increasing coherence (ideological, not logical) of the “liberal” wing. This graph captures the difference between the wings:

The record of the past 6 terms (2012-2017) is clear. The “liberals” stick together much more often than the “conservatives”. Perhaps that will change with the replacement of Kennedy by (one hopes) a real conservative.