Credibility is key---the court will moderate to regain public confidence.

That doesn’t mean Democrats should unilaterally disarm, however. It may sound counterintuitive, but serious threats to name more justices to the court could lead to a more moderate and legitimate court.

A credible threat to pack the court would create powerful incentives for the current justices to moderate their views on important issues and preserve the court’s credibility.

That is what happened in 1937, when President Franklin D. Roosevelt threatened to add six justices to neutralize the court’s conservative majority. Faced with the prospect of serving the rest of his career in the minority of a delegitimized court, Justice Owen Roberts became more restrained in his antagonism to the New Deal.

The path to a self-correcting court is steeper today than it was in 1937. Conservatives held a bare 5-4 majority then; with Amy Coney Barrett on the bench, two conservative justices would have to rein in their views. Moreover, today’s court faces a wider array of deeply divisive social and political controversies. How can the court decide these cases in a way that earns the public’s approval?

In a forthcoming law review article, I identify a promising approach supported by a surprisingly rich tradition of the court’s own precedents: In hard cases, rather than relying on theories like originalism or living constitutionalism, the court often rules against the side that has the strongest options for avoiding harm after defeat. By ensuring that the losing group can protect its interests in other ways, the court minimizes the harmful effects — and backlash — from its decisions. I call this approach the “least harm” principle.

Significantly, three of the court’s conservatives followed this very approach to decide some of the last term’s most important cases. Two of these decisions involved subpoenas seeking financial records about President Trump. Chief Justice John Roberts wrote them; he was joined by Justices Neil Gorsuch and Brett Kavanaugh.

The court ruled against the president in Trump v. Vance, permitting a New York prosecutor’s subpoena to proceed. It did so precisely because Mr. Trump could “avail himself of the same protections available to every other citizen” by challenging the subpoenas as overbroad or in bad faith.

By contrast, the court ruled in Mr. Trump’s favor in a second case involving subpoenas issued by the Democratic-controlled House of Representatives. Those subpoenas were challengeable, the court explained, to the extent that the House had better ways to obtain the information it needed, either from other sources or by subpoenas that were narrower in scope.

Justice Gorsuch’s landmark opinion protecting L.G.B.T. employees from discrimination also drew on the least harm principle by explaining that religious employers who oppose the ruling might avoid harm by seeking exemptions under the Religious Freedom Restoration Act or Free Exercise Clause.

And Chief Justice Roberts followed the same approach in the DACA case, which blocked the Trump administration’s attempt to end a program protecting roughly 700,000 young immigrants known as Dreamers from deportation. The court noted that the administration could try to rescind DACA again, so long as it offered a more well-reasoned explanation for doing so.

Each of these cases raised legal questions on which reasonable people disagreed. Given this uncertainty, the Supreme Court respectfully acknowledged each side’s interests and ruled against the group with the best strategies for minimizing harm from its loss — leaving the losing side little reason to assail the court.

No wonder, then, that the court concluded last term with its highest public approval rating in over a decade, including the narrowest partisan gap Gallup has ever recorded between Republicans (60 percent) and Democrats (56 percent). Each side’s losses felt temporary — and thus bearable — precisely because the court’s decisions reminded them that there were other ways to protect their interests.

Of course, progressives won’t win every case before a harm-minimizing Supreme Court. But the primary goal shouldn’t be liberal victory by any means necessary. That is the attitude that conservatives weaponized.

Instead, progressives should play the long game. By threatening to pack the court, they can put much-needed pressure on the conservative justices to moderate their views and to consider which side will suffer the least harm — and thus earn the public’s confidence.