In a recent article in the New York Times Adam Liptak describes the increasingly partisan splits on the Supreme Court. More than at any time in its history, he argues, the divisions in cases follow partisan as well as ideological alignments. Thus, today the five justices appointed by Republican Presidents (the Chief Justice, Scalia, Kennedy, Thomas and Alito) vote consistently more conservatively than those appointed by Democratic Presidents (Ginsburg, Breyer, Sotomayor, Kagan).
For the moment I will accept Liptak’s statistics and focus on his explanations. Liptak argues that partisan polarization is the result of increased polarization more generally, as Republicans and Democrats move to become cohesive ideological parties, distant in their policy preferences. Moreover, Liptak argues Presidents have become better at predicting justices’ votes. These factors are certainly relevant, but I think they miss one important change. Originalism and its often close cousin in statutory interpretation—textualism— today create a larger gulf in jurisprudential approaches to the Constitution and statutes between Republican and Democratic appointees.
There was not such a consistent jurisprudential chasm in the Court for much of the latter part of the twentieth century. There were no originalists on the Court when Scalia joined it. Thomas then became another powerful originalist voice. While Alito and Roberts are not pure originalists, the original meaning of the text has a strong pull for them even if precedents restrain the extent of its power. Their opinions on the commerce clause in Sibelius are excellent examples of the power of the text; the Democratic appointees did not even substantially respond to the originalist arguments.