Why we have the most polarized Supreme Court in history

The unexpected passing of Justice Antonin Scalia has had and will have enormous ramifications across the American polity.

Prior to his passing on February 13, hardly a word was mentioned about the Supreme Court in any of the presidential debates. In contrast, subsequent debates mentioned the words “court” or “justice” more than 20 times.

And barely an hour after Scalia’s passing, Senate Majority Leader Mitch McConnell declared that no replacement should be named until after the 2016 election.

As to the court itself, the impacts of Scalia’s passing could be significant, including a reprieve for affirmative action (Fisher v. Texas), an inability to prohibit mandatory union dues by public employees (Friedrichs v. California Teachers’ Association) and greater leeway under the Second Amendment to regulate guns (Voisine v. United States).

In fact, if a Democratic president gets to appoint the next justice, the doctrine that the Second Amendment provides an individual right to bear arms, and not just a right of state militias (United States v. Heller), could fall, as could the doctrine that campaign contributions by individuals and corporations are a form of speech protected by the First Amendment.

My confidence in this assertion is based on the fact that in recent times, unlike any time in our history, we are unlikely to see conservative Democrats or liberal Republicans on the Supreme Court.

That’s because the Supreme Court is more polarized politically than it’s ever been. If historical trends continue, the next Supreme Court justice will not be a moderate, but a person with strong ideological views.

Different times

For the first time in the Supreme Court’s history, every Republican on the court is to the right of every Democrat, as measured by the Martin-Quinn score.

I submit that at least part of the reason for this polarization on the court is the polarization in the Senate.

Because justices are nominated by the president and confirmed by the Senate, the impact of party on the choice of justices should roughly reflect the amount of partisan division at the time of the justices’ appointment. And indeed, we have seen this in decades past.

For example, the 94th Senate confirmed John Paul Stevens, a liberal Republican, at a time when there were many liberal Republicans in the Senate, such as Jacob Javits (New York) and Edward Brooke (Massachusetts).

Similarly, the 92nd Senate confirmed Lewis Powell, a conservative Democrat, at a time when conservative Democrats such as John Stennis and James Eastland (both Mississippi) were fairly common.

Given growing party polarization in Congress over the last 30 years, we should also expect a relatively tighter fit between party and voting behavior on the court in 2010 than we would find in 1994. But has that actually been the case?

Spreading partisanship

Consider the following evidence. I start by examining the overlap between partisanship in the 98th Senate (1983-84) and the justices serving 10 years later – that is, the 1994 term of the court. With new appointments every few years a polarized Senate would not have an immediate effect on the court, but over time the impact would grow.

As the graph below shows, there was a fair amount of overlap in partisanship in the 98th Senate as represented by ideal points, a common way to measure political leanings.

Figure 1: Ideal points (liberal to conservative) by party 98th Senate with Republican senators in black, Democratic senators in white.

Ten years later, we find, based on commonly used ideology scores of the justices, Republican Justice John Paul Stevens to be the most liberal member of the court, while Republican Justice David Souter falls to the left of Democratic Justice Stephen Breyer.

Figure 2. Ideal points (liberal to conservative) of the justices by party, 1994 term. Legend: nominees by Republican presidents in CAPS.Andrew Martin and Kevin Quinn

Then I look at the partisanship in the 107th Senate (2001-03) and the justices serving on the 2010-11 term. By the 107th Senate, we observe far less overlap between Republicans and Democrats.

Ideal points (liberal to conservative) by party, 107th Senate with Republican senators in black, Democratic sSenators in white.

The increasing homogeneity of the Republican Party since the 1980s, combined with the battle cry “No More Souters,” should make it increasingly difficult for a Republican president to nominate a Supreme Court justice who overlaps ideologically with Democratic justices.

Has this happened? While Harriet Miers’ lack of qualifications no doubt hurt her chances for confirmation, her failure was certainly aided and abetted by conservatives who were not certain about her ideological purity, given her ambiguous statements about abortion rights as well as her past political contributions to Democrats Albert Gore and Lloyd Bentsen. In fact, conservative commentator Charles Krauthammer laid out her eventual exit strategy. (She eventually withdrew her nomination.)

To a lesser extent, liberal Democrats vocally expressed some dissatisfaction that President Obama’s choice to replace Justice Stevens, Elena Kagan, was not sufficiently liberal. While Democrats had no intention of voting against Kagan, the carping about her nomination was certainly a signal from liberal Democrats to President Obama to resist further movement toward the political center in future nominations.

The make-up of today’s court does indeed reflect a partisan legislature. Ten years after the 107th Senate, and given Justice Stevens’ retirement, we no longer observe any overlap between Republicans and Democrats on the court, as seen in the chart below. The five Republicans on the court (in CAPS) place above the four Democrats.

To be sure, this complete segregation by party exists only because of the retirement of Justice Stevens in 2010. But Justice Stevens, from the moderate wing of the Republican Party, was appointed at a time when there were many moderates and even some liberals in the Republican Party.

My model of course cannot predict how long partisan-ideological aberrations such as Stevens will remain on the court. But as long as the partisan-ideological stance of the Senate remains, the Supreme Court will continue, with a certain time lag, to gain justices on either ends of the partisan spectrum.

Jeffrey Segal receives funding from National Science Foundation.