This month’s argument in Dobbs v. Jackson Women’s Health Organization suggested that a majority of the Supreme Court is ready to overrule Roe v. Wade and allow states to impose strict limits on abortion. As many observers noted, the court’s arguments showed clearly that six Republican appointees control the court, leaving the three Democratic appointees to fight rearguard actions.
How long will the conservative justices control the Supreme Court? We ran a simulation to predict the ideology of the justices through the year 2100; we assume that the existing structure of life tenure and a nine-member court remains in place. While no one can predict the future with certainty, our analysis suggests that conservative justices will control the court for at least the next three decades.
How we did our research
Our simulation tries to predict the ideology of future justices, much as other scholars have in the past. We started with the current justices and projected the court forward through the year 2100. For every year, we calculated the probability a justice will leave the court through death or retirement, based on age. We assumed that justices, especially older ones, would be more likely to time their retirement strategically, when the president is of the same party.
Using actual past election results as a guide, for each year, we calculated the probability that the president would be a Democrat or a Republican. In the simulations, we assumed that all nominees would be confirmed by the Senate, without the sort of holdup that Senate Republicans imposed on President Barack Obama’s nominee to replace Antonin Scalia. Finally, we assume that each new justice would be a reliable ideologue, meaning that Republican-appointed justices would vote conservatively and vice versa. That last assumption is consistent with our past research showing that presidents in recent decades have emphasized appointing reliable justices and avoiding “stealth justices” such as Republican-appointed Justice David Souter, who ultimately voted with the more liberal justices.
In technical terms, we assumed that all the possible ways in which a justice could rule fit on a single spectrum ranging from left to right, and that each justice had an “ideal point,” a specific position on that left-right spectrum that reflected her or his ideological preferences, so that for each year there was a “court” of nine justices, arrayed from those who voted more liberally to those who voted more conservatively.
The justice with an ideal point in the “middle” of this spectrum would be the median justice, with four justices each to the left and right. The ideology of the median justice gives us a useful sense of the ideological center of the court, and hence who is likely to win or lose a given case. For example, standard measures suggest that conservative Justice Brett M. Kavanaugh is currently the median justice. He voted with the majority in 97 percent of the court’s cases last term.
We ran the simulation 1,000 times, giving us 1,000 “courts” in every year, allowing for some variation in new justices’ ideal points across the simulations, both because the party making the appointment will vary and because there is internal ideological variation among Democratic-appointed judges as well as among Republican appointed judges (though, on average, Democratic justices will always be more liberal than Republican justices). For each simulation, we calculate the location of the median justice. The figure below summarizes our findings.
Here, just as in election simulations, saying that there is a higher chance that the median justice is conservative means saying that we see this happening in more of the simulations that we have run. When the bars are higher on the right, the median justice is conservative in more of the simulations we run, suggesting that there is a higher probability that they will indeed be conservative. When the bars are higher on the left, the opposite is true.
Our results are unambiguous. In the early decades, the medians obviously tilt heavily conservative, suggesting that conservatives will likely control the court through the 2040s. Only in the 2050s do the distributions become roughly symmetrical, meaning that there’s an equal chance the court’s median justice will be liberal or conservative.
The Supreme Court is likely to remain conservative until the 2050s
Why is the Supreme Court likely to remain conservative for another 30 years? First, justices now sit on the court much longer than they used to. The current conservative justices are likely to serve for many years, especially Trump’s three appointees, Neil M. Gorsuch, Brett M. Kavanaugh and Amy Coney Barrett, none of whom were older than 52 at the time of appointment. They will probably serve at least through the late 2030s.
If justices strategically retire under a president of the same party, seats are unlikely to flip from one party to the other. The other three Republican appointees are significantly older, but likely to serve at least until about 2030. If they retire earlier, when there’s a fellow Republican in the White House, they will be succeeded by another conservative. As a result, the median’s ideological position is less likely to change than in earlier eras, when the nominating party’s ideology was less likely to coincide with their judicial appointments.
Of course, all these calculations are based on assumptions, not certainties. It’s certainly possible that the court will become more liberal sooner than we project — but only if several of the conservative justices unexpectedly retire or die when there’s a Democratic president.
It’s also possible that Democrats could alter the Supreme Court by imposing term limits, adding more justices, or some other shift. After the oral arguments in Dobbs, many Democratic senators said the time had come to consider reforming the court. But with the House and Senate so closely divided and midterm elections approaching, such changes seem very unlikely.
Roe may be just the first of many liberal landmark precedents to fall in the coming years.
Charles Cameron is a professor in the department of politics and the School of Public and International Affairs at Princeton University.
Jonathan P. Kastellec (@jkastellec) is an associate professor in the department of politics at Princeton University.
Note: Updated Oct. 5, 2023.