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Words used in coverage of Musk’s Twitter buy. Purple color indicates words found in analysis from both sides; blue and red indicates words found only in analysis on the left and right, respectively. Elon Musk’s acquisition...

Median Judicial Ideology of Supreme Court Justices since 1937. Source: Martin-Quinn Scores
As the U.S. Senate prepares to vote on whether to confirm U.S. Circuit Judge Ketanji Brown Jackson, President Joe Biden’s first nominee to the U.S. Supreme Court, news outlets on the left and right are divided on coverage.

If confirmed, Jackson would replace Justice Stephen Breyer, who is retiring after 28 years on the bench. Nominated by President Bill Clinton, Breyer is considered one of the liberal Justices on the Court, such as by voting repeatedly to affirm access to abortion.

How would the confirmation of Judge Ketanji Brown Jackson affect the judicial ideology of the Supreme Court?

Conservative Justices outnumbered liberal justices by 6-3 at the conclusion of the October 2020 Supreme Court term, based on their Martin-Quinn scores, which is an analysis of a dataset of the Justice’s voting record during a term, based on how often they agree or vote with each other. The score following the term placed Justice Breyer as the second-most liberal member of the Court.Like any similar statistical model, it should be noted that Martin-Quinn scores has some limitations in how it measures bias. For one, it looks solely at the vote from each Justice in each case during a given year – some may argue that judicial ideology should factor in oral arguments and the fact that the Court has discretion over the cases that it will hear. Furthermore, not all outcomes of Supreme Court cases can be easily described as “liberal” or “conservative” – bias is subjective, and there is no concrete definition of what “center” or “moderate” is. 

(Side note: Here at AllSides, our media bias ratings system is designed to reflect the average judgment of all Americans across the political spectrum if they had the opportunity to read and evaluate the content. That means that a “Center” rating from AllSides is intended to reflect how all Americans on average would rate that content.)

How The Ideology of the Supreme Court Has Shifted Over Time

Since the 1940’s, the Supreme Court has most often been conservative in ideology, according to the Martin-Quinn scores. A couple of exceptions include a swing in liberal ideology during and after the Civil Rights Era, and slight lean-liberal ideology during President Obama’s second term in office. Since President Donald Trump’s tenure in office, the Court has trended further conservative, on average, in part due to the former President’s three confirmations.

The below graph is based on the median Justice during each respective term. Negative values indicate liberal ideology, and positive values indicate conservative ideology.

The individual ideology of Justices also tends to shift with time. In the graph above, red lines represent Justices nominated by a Republican president and blue lines represent Justices nominated by a Democratic president. Dotted lines indicate Justices who no longer serve on the Court.

In Justice Breyer’s 28 years on the Court, he has become more liberal over time, along with Justice Sotomayor and Chief Justice Roberts. Justice Alito has become more conservative with time, and Justice Thomas has remained relatively stagnant over the last decade.

Public Perception of the Ideology of the U.S. Supreme Court: Too Liberal or Conservative?

Public perception of Supreme Court ideology has also shifted over time, according to Gallup (Center bias). Unsurprising to some, more Americans perceived the Court as “too liberal” during President Obama’s tenure in office and as “too conservative” while President Trump was in office. Overall, however, Americans have consistently perceived the Court’s judicial ideology as “about right” — in other words, relatively nonpartisan or balanced.

According to a September 2021 YouGov/The Economist (Lean Left bias) poll, just one in four (24%) U.S. adults believe that the Supreme Court is fair and impartial – more Americans believe the Court is biased against Democrats (29%) than biased against Republicans (19%).

A Pew Research Center (Center bias) survey in January 2022 found that 48% of U.S. adults view the Supreme Court as “middle of the road” ideologically, while 38% view it as “conservative” and about 1 in 10 (9%) view the Court as “liberal.”

To that end, it remains to be seen how public opinion will shift after Judge Ketanji Brown Jackson joins the Supreme Court, if confirmed. The Supreme Court will also be ruling on Dobbs v. Jackson Women’s Health Organization this term – a decision that may result in overturning the precedence of Roe v. Wade – which may further shift public opinion of the ideology of the Supreme Court.

Read more about the U.S. Supreme Court on AllSides.

Andrew Weinzierl is the Research Assistant & Data Journalist at AllSides. He has a Lean Left bias.

This piece was reviewed by Antonio Ferme, AllSides Weekend Editor (Center bias), Managing Editor Henry A. Brechter (Center bias), News Research Intern Ethan Horowitz (Lean Right bias), and CEO John Gable (Lean Right bias).