Yet, jurisprudence scholarship does suggest that something has changed: the court is becoming more partisan. According to a 2009 study conducted by Richard Posner and William Landes, John Robert’s court has the
most partisan bench in history. The rising wave of
partisanship that has swept through Congress and the White House is matched by the growing polarization of the Supreme Court.

How the Supreme Court Justices Line Up Source: Pew Research Center
The growing polarization manifests itself in the long string of 5-to-4 decisions made by the Roberts Court. In two of the most recent courts, more than 20 percent of all decisions decided by 5-to-4 votes, and that means that the rulings that have the greatest potential to influence the lives of the American public are regularly decided by the narrowest margin. Furthermore, legal scholars consider those narrow 5-to-4 decisions to be the most political, while research shows that those rulings often overturned by later courts. Even more importantly, they do not convey the same moral authority as more unanimous opinions.
That concerns Chief Justice John Roberts, whose court has decided more cases by the 5-to-4 margin than any other. “I do think the rule of law is threatened by a steady term after term after term focus on 5-4 decisions,” Roberts
told The New Republic‘s Jeffrey Rosen in 2006. “I think the Court is ripe for a similar refocus on functioning as an institution, because if it doesn’t, it’s going to lose its credibility and legitimacy as an institution.” During his 2005 confirmation hearing he also told lawmakers that he would attempt to implement “a greater degree of coherence and consensus in the opinions of the court,” citing former Chief Justice Earl Warren’s leadership in
Brown v. Board of Education as an example.
The Roberts Court’s partisan, 5-to-4 decisions have upheld the constitutionality of the Affordable Care Act’s individual insurance mandate as well as an individuals’ right to
gun ownership, limited class-action suits as well as an employee’s right to file a pay discrimination, and allowed unlimited corporate and union campaign spending. Votes on immigration, arbitration rights, voting rights, and the legality of legislative prayer were similarly divided.
Unsurprisingly, analysis conducted by Posner and Landes showed that the more ideologically polarized the Court is — meaning the greater the divide between the most conservative justice and the most liberal justice — the more often cases are decided by a 5-to-4 margin. This court is also the most conservative since the New Deal. Posner and Landes ranked 43 Supreme Court justices who served between 1937, when dissents were rare and justices rarely divided along party lines, and 2006, in terms of political ideology. They found that four of the five most conservative justices — Clarence Thomas, Antonin Scalia, John Roberts, Samuel Alito, and William Rehnquist– were sitting on the bench as of 2005, while the current liberal-leaning justices do no place in the top five. Ruth Bader Ginsburg was the only sitting judge to rank among the top ten most liberal justices.