Q&A – Ranking Supreme Court Justices from Most Conservative to Most Liberal

Q&A – Ranking Supreme Court Justices from Most Conservative to Most Liberal 

Each day I feature a listener question sent by one of these methods.   

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Today’s entry: @brianmuddradio Please rank SCOTUS justices from conservative to liberal. 

Bottom Line: Ask and you shall receive. Today’s Q&A is a follow-up to yesterday’s Q&A – in which I broke down how often Supreme Court justices agree with each other on rulings...which, at 71% with the current court, is probably a lot more often than most think. But with that said, there are stark ideological differences between the justices which any court observer, even casual observers, are familiar with. So, about those as we dive into today’s Q&A. 

Ranking Supreme Court justices based on ideological splits includes some degree of subjectivity, just as is the case with members of Congress. With that said, the most frequently cited source of ideological splits comes from what is known as the Martin-Quinn scores. Andrew Martin and Kevin Quinn are political scientists who created scores based on SCOTUS votes based on these factors: 

• Ideological Spectrum: The scores rank justices from liberal to conservative, with zero representing a neutral or moderate position 
• Dynamic Measurement: Reflects changes in justice's voting patterns over time 
• Votes: The scores are derived from a justice's voting record in cases, using a statistical model that estimates their ideological position 
• Dynamic Item Response Theory: Allows for the possibility that justice's ideology can change over time 
• Applications: Determines the ideological makeup of the court 

Often when you hear people rank justices on ideological leanings, it’s the Martin-Quinn scores that are the basis for them. Based on the most recent available data combined with qualitative analyses of judicial philosophies, here is the ranking of the current nine justices from most conservative to most liberal: 

1. Clarence Thomas (Martin-Quinn score: 3.05): Consistently votes in a conservative direction. Known for originalist interpretations and skepticism of federal overreach 
2. Samuel Alito (Martin-Quinn score: 2.59): Most often aligns with Thomas, Often authors conservative opinions like Dobbs v. Jackson, which overturned Roe v. Wade 
3. Neil Gorsuch (Martin-Quinn score: 1.12): Libertarian-leaning but firmly conservative. Is more closely aligned with Thomas and Alito than the less conservative justices in the “conservative bloc”. 
4. Amy Coney Barrett (Martin-Quinn score: 0.68): Conservative, particularly on religious liberty and abortion, but sometimes joins liberals in unexpected coalitions. Her ideology is close to Kavanaugh’s but less predictable. 
5. Brett Kavanaugh (Martin-Quinn score: 0.52): Center-right, often a swing vote but generally aligns with conservatives. His voting has shifted rightward since joining. 
6. John Roberts (Martin-Quinn score: 0.43) - Chief Justice, often takes an incremental approach, making him the court’s most moderate justice. in some cases. He occasionally sides with liberals to preserve institutional traditions. 
7. Ketanji Brown Jackson (Martin-Quinn score: -1.70): Liberal, but less so than Sotomayor and Kagan in her first term – though the most liberal most recently  
8. Elena Kagan (Martin-Quinn score: -2.06): Liberal, known for pragmatic and persuasive opinions. She often seeks consensus, authoring unanimous or near-unanimous decisions, but is the trend setter with the liberal wing 
9. Sonia Sotomayor (Martin-Quinn score: -4.14): The most liberal justice (though second to Jackson most recently), frequently dissenting in conservative-majority rulings and advocating for civil rights, criminal defendants, and individual liberties against government 

So, there’s the breakout. Notably, the most liberal Justice, Sotomayor is considerably farther to the left, than the most conservative Justice Thomas is to the right. Also, the “conservative bloc” with an average 1.4 score, is far less conservative than the “liberal bloc” with an average score of –2.6 happens to be.