This long page consists of four parts: Lines of Succession, Ideological Alignment, Polarization (which comes at alignment with different metrics), and Judging the Justices: The Thomas Standard (explained below).
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 2018. (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 (in non-unanimous cases) with members of own wing/percentage disagreement (in non-unanimous cases) with members of opposite wing.
The wings are the “conservative” wing, whose members during the 2005-2018 terms were and are Alito, Gorsuch, Kavanaugh, Kennedy, Roberts, Thomas, and Scalia; and the “liberal” wing, whose members in the same span of time were and are 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’s slippage in the 2011-2015 terms has been partially reversed. But his foolish attempts to “protect” the Court from accusations of political bias (e.g., the Obamacare and census cases), have rightly caused real conservatives to be wary of him.
Gorsuch started out strongly in his abbreviated 2016 term (he joined the Court in April 2017), but seems to be slipping away from the “conservatives”, at least with respect to criminal cases.
Kavanaugh’s record in his first term aligns him squarely in the “conservative” wing.
What’s most striking about the preceding graphs, other than Kennedy’s marked departure from the “conservative” wing after the 2010 term and sudden return to it in his final term, is the increasing coherence (ideological, not logical) of the “liberal” wing. This graph captures the difference between the wings:
With Kennedy’s aberrant terms out of the way, the “conservative” wing seems to be as coherent as the “liberal” wing — though the presence of Gorsuch and Roberts makes the “conservatives” less monolithic than the “liberals”.
The statistics yield an index of polarization (P) for each justice, by term:
P = maximum percentage of non-unanimous cases in which a justice disagreed with any other justice during the term
A slight upward trend over the past 14 terms? Perhaps. But there has definite movement toward polarization since Kennedy’s peak defection terms (2014-2015). Trend or no trend, it’s clear that there is and has been a great deal of polarization among most of the justices.
I would be pleased no end if the Supreme Court consisted of Clarence Thomas and eight clones of him. It seems to me that Justice Thomas has been the most faithful adherent of the Constitution among all of the justices who have served on the Court since I became interested in its doings more than 50 years ago. Taking Thomas as the standard for constitutional judging, it is possible to grade some of the other justices who have served with him, including all of his present colleagues.
Reversing the numbers discussed thus far, so that degree of disagreement becomes degree of agreement, and focusing on the extent to which other justices agree with Thomas non-unanimous cases, I obtain the following statistics:
Scalia was a stalwart conservative, albeit somewhat quirky inn criminal cases, as is Gorsuch. Alito remains a stalwart, and Kavanaugh shows promise. Roberts continues to slip away. Breyer, Ginsburg and Sotomayor keep digging themselves deeper into leftist position. Kagan, though on the left, is relatively moderate by comparison with her three “liberal” colleagues.