Justice League: The members of today's Supreme Court, far from calling balls and strikes, are very much in the partisan game.

• Author: Graber, Mark A.

The Company They Keep: How Partisan Divisions Came to the Supreme Court

by Neal Devins and Lawrence Baum

Oxford University Press, 264 pp.

Midway through his Supreme Court confirmation hearings, Brett Kavanaugh switched teams. He began as a potential player for the Supreme Court Nine in the nonpartisan law league, telling the Senate Judiciary Committee on the first day of hearings, "A good judge must be an umpire--a neutral and impartial arbiter who favors no litigant or policy." He ended a faithful member of a Federalist Society squad in the partisan politics league. The investigation of Christine Blasey Ford's allegations of sexual assault, he later raved to the same committee, was "a calculated and orchestrated political hit, fueled with apparent pent-up anger about President Trump and the 2016 election," as well as "revenge on behalf of the Clintons and millions of dollars in money from outside left-wing opposition groups." Gone was any air or even pretense of nonpartisanship. Kavanaugh appealed exclusively, and successfully, to the Republican Party.

Neal Devins and Lawrence Baum's new book, The Company They Keep, seeks to explain why every member of the contemporary Supreme Court plays in the partisan politics league. The period following the retirement of Justices David Souter and John Paul Stevens is the first time in history that Supreme Court voting blocs correspond perfectly with the party of the appointing president. Bipartisan majorities and bipartisan dissents occurred in every major case decided by a fractured Court during the nineteenth and much of the twentieth centuries. Republican appointee Harry Blackmun and Democratic appointee Thurgood Marshall joined hands in the Roe v. Wade majority, as did Republican appointee William Rehnquist and Democratic appointee Byron White in the dissent. Hardly any Roberts Court decisions feature both bipartisan majorities and bipartisan dissents. Decisions like Trump v. Hawaii, in which the five conservative Republican appointees outvoted the four liberal Democratic appointees to uphold President Trump's travel ban, are the norm.

Devins and Baum point to the usual suspects when explaining the increased partisanship of the Supreme Court. The Court is more partisan and polarized because both politics and the elites who disproportionately determine its course--and staff the federal judiciary--are more partisan and polarized. Contemporary presidents pay more attention to ideology when selecting...