Supreme Court Ideological Patterns Shift in Closely Divided Cases

Washington D.C. — An examination of Supreme Court merits decisions since Justice Ketanji Brown Jackson joined the bench four years ago indicates that justices' ideological voting patterns become more pronounced in closely divided cases. The analysis, which categorized votes as either conservative or liberal outcomes, found that the court's ideological structure shifted when focusing solely on contentious rulings.

The study compared three sets of cases: the full range of merits decisions, a subset including only 5-4 and 6-3 votes, and a third subset that excluded specific 6-3 decisions where all six Republican-appointed justices voted together against the three Democratic-appointed justices.

Chief Justice John Roberts, along with Justices Amy Coney Barrett, Brett Kavanaugh, and Neil Gorsuch, showed an average distance of approximately 4.3 percentage points from a 50/50 conservative-liberal voting record across the full merits docket. When the analysis narrowed to include only 5-4 and 6-3 decisions, this average distance increased to 16.8 percentage points. However, when the 23 specific 6-3 cases, where the six Republican appointees formed a unified bloc, were removed from the contentious cases, the average distance for these four justices decreased to approximately 4.0 percentage points.

Conversely, Justices Samuel Alito and Clarence Thomas consistently voted further to the conservative side, while Justices Sonia Sotomayor, Elena Kagan, and Ketanji Brown Jackson consistently voted further to the liberal side. Across all merits cases, the average justice recorded approximately a 10.5% deviation from a balanced voting record. This deviation rose to 26.8% when considering only 5-4 and 6-3 cases.

Justice Alito's voting record, for instance, showed a 15.5 percentage point conservative leaning across all merits cases, increasing to 41.0 percentage points conservative in closely divided cases. Justice Thomas's conservative leaning moved from 12.1 points to 30.6 points in such cases. On the liberal side, Justice Sotomayor's record shifted from 17.5 points liberal to 36.6 points liberal in closely divided decisions. Justice Kagan's record similarly moved from 15.7 points liberal to 36.6 points liberal, and Justice Jackson's from 16.3 points to 29.1 points liberal.

For Justices Kavanaugh, Roberts, Gorsuch, and Barrett, their distances from a 50/50 record also increased in closely divided cases. Kavanaugh moved from 5.1 points conservative to 21.6 points conservative; Roberts from 3.4 points to 17.2 points conservative; Gorsuch from 6.2 points to 15.7 points conservative; and Barrett from 2.5 points to 12.7 points conservative.

When the 23 pure ideological 6-3 cases were removed, the ideological distances for Roberts, Kavanaugh, Barrett, and Gorsuch substantially reduced. Roberts's voting record in the remaining close cases became evenly split, with 22 conservative and 22 liberal votes. Kavanaugh's conservative leaning dropped from 21.6 points to 6.8 points. Gorsuch moved from 15.7 points conservative to 2.3 points liberal, and Barrett moved from 12.7 points conservative to 6.8 points liberal in this specific subset of cases.

The analysis also identified recurring alternative coalitions in cases that did not involve the unified six Republican-appointed justices. In 10 of the 44 remaining closely divided cases, Justices Roberts, Sotomayor, Kagan, Kavanaugh, Barrett, and Jackson formed the majority, with Justices Thomas, Alito, and Gorsuch in the minority.

Examples include the 2023 case *Moore v. Harper*, where Roberts, Sotomayor, Kagan, Kavanaugh, Barrett, and Jackson rejected a broad theory regarding state legislative authority over federal elections. Similarly, in *Allen v. Milligan* in 2023, Roberts and Kavanaugh joined the three Democratic appointees in a 5-4 decision affirming a lower court ruling on Alabama's congressional map. In 2024's *Harrington v. Purdue Pharma*, Gorsuch wrote the majority opinion joined by Thomas, Alito, Barrett, and Jackson, with Kavanaugh dissenting alongside Roberts, Sotomayor, and Kagan.

This pattern indicates that while a significant portion of contentious cases show a clear ideological division along party lines, other closely divided decisions reveal varied alignments among the justices.