Will Democratic presidential candidate Joe Biden pack the Supreme Court if he wins? That’s a hot topic as the news media cover the election and the Senate’s confirmation process for nominee Amy Coney Barrett. Pundits and political players alike are debating whether Biden, his running mate, Sen. Kamala D. Harris (D-Calif.), and other Democrats should add seats to the Supreme Court as political revenge for Republicans’ about-face on confirming election-year nominees.

Why is this court-packing proposal suddenly so widely discussed? And why was the Republican Senate comfortable flipping its position on election-year appointments?

Americans are far less willing to defend the Supreme Court’s stability and integrity than many political scientists believe — especially now, at a time when they’re so polarized ideologically. That’s what we show in our new book, “Curbing the Court: Why the Public Constrains Judicial Independence.” We found that citizens show substantial support for “court-curbing” — measures to undermine judicial independence and power — when the court rules against their political team. As a result, elected officials know their supporters are likely to cheer on any attacks on the court as is, and to reward them when they succeed.

Do Americans really want to protect the Supreme Court?

Our research challenges conventional wisdom among political scientists that the American public is the “guardian of judicial independence.” In this view, the public holds the court in high esteem, rooted in the court’s reputation for procedural fairness and upholding democratic values, and punishes elected officials for attempts at curbing, such as stripping the court’s jurisdiction, failing to comply with rulings or politicizing appointments.

In contrast, we found that citizens are only weakly principled: They say they support long-standing norms and institutions in the abstract but are willing to attack them in practice when it serves their partisan beliefs. That is, Americans will support court-curbing if they disagree with the court’s decisions. Partisan polarization — with adherents of each party growing farther apart ideologically — makes this stronger. Unlike other political scientists who’ve focused on this, we argue that attitudes toward the Supreme Court are affected by such political polarization.

Here’s how we did our research

We analyzed data from seven national surveys of American adults — including experimental, cross-sectional and longitudinal studies — spanning 2005 to 2017. We measured support for a variety of court-curbing actions, from narrow attacks (such as measures to overturn a judicial ruling) to broad ones (such as reducing the court’s independence and its ability to decide issues).

First, we found that the court’s reservoir of goodwill in the public is not as wide and deep as some scholars maintain. We found considerable support for making the court less independent, for example, through stripping the court’s jurisdiction, holding retention elections for justices or instituting nationwide referendums to overturn controversial decisions.

Second, we found disagreement with the court’s rulings strongly increases support for court-curbing. Citizens care more about decision outcomes than the process by which they are reached. Third, partisan polarization makes policy disagreement more important. When citizens see the parties as sharply divided, they are much more willing to attack the court on behalf of their own side.

Our results suggest that an accumulation of uncongenial rulings — or expecting these in the future — leads people to support fundamental changes to bring the court more in line with their beliefs.

Why court-curbing matters now

The Supreme Court’s power in U.S. government depends on politicians deferring to its rulings even when they disagree. As Justice Elena Kagan said last year in an address at Princeton: “Every single one of us needs to realize how precious the court’s legitimacy is. You know we don’t have an army. We don’t have any money. The only way we can get people to do what we think they should do is because people respect us.”

Elected officials will respect the court’s authority when they fear public backlash for what they might do. Without that, they have a strong incentive to undermine the institution for political gain. We see this in Senate Republicans’ successful refusal to act on President Barack Obama’s nomination of Judge Merrick Garland in 2016, arguing that was an election year only to reverse themselves while people are voting in the 2020 presidential election. And we see it in calls from the left for court-packing to counterbalance three Trump appointments. Such tit-for-tat battles result from, and contribute to, the American public seeing the court as a vehicle for political gain.

A long line of political science research argues that judges are strategic and issue rulings based on what they believe legislators and the public are willing to accept. If the American public defends judicial independence, the court can issue rulings based on sincere readings of the law. If the public cares more about policy and partisanship, by contrast, the court tries to avoid backlash by issuing rulings that are closer to what citizens, Congress and the president want. That attention to legitimacy arguably drives the court to be more moderate, so that neither side attacks the court’s powers.

For example, some argue that Chief Justice John G. Roberts Jr. has moderated his decisions to protect the court’s legitimacy. That will be harder — if not impossible — to do if Trump and Senate Republicans successfully install a sixth conservative justice. In turn, this will further lead Americans to see the court as political, encouraging Democrats to make changes and thus continuing the cycle of political polarization.

Brandon L. Bartels is an associate professor of political science at George Washington University. @blbartels

Christopher D. Johnston is an associate professor of political science at Duke University. @JohnstonCD