Supreme Court Chief Justice of the United States John G. Roberts Jr. in December 2018 at the U.S. Capitol in Washington. (Jabin Botsford/The Washington Post)

Leah Litman is an assistant professor at the University of California at Irvine School of Law. Joshua Matz is a lawyer at Kaplan Hecker & Fink LLP and publisher of the Take Care legal blog. Steve Vladeck is a professor at the University of Texas School of Law.

It is illegitimate to consider legitimacy. So say many conservatives who seem terrified that Chief Justice John G. Roberts Jr. might care about public perception of the U.S. Supreme Court. Haunted by his vote upholding the Affordable Care Act — a vote they view as unprincipled — they insist that only a weak-willed, weak-kneed judge would ever deviate from right-wing orthodoxy to preserve the court’s legitimacy. They urge the chief justice to stick with the conservative party line and rise above the supposedly cynical warnings that this term’s biggest cases could harm the judiciary.

These arguments are profoundly hypocritical. Conservative lawyers and judges have long raised concerns about judicial legitimacy to protest progressive rulings on abortion, the death penalty, same-sex marriage, partisan gerrymandering and many other issues. In Obergefell v. Hodges, for instance, then-Justice Antonin Scalia warned that the court’s decision recognizing a constitutional right to marriage equality “has to diminish this Court’s reputation for clear thinking and sober analysis.”

But that was then, and this is now. Calls to be mindful of judicial legitimacy are passe; conservatives demand activism of the court they believe they have captured. No matter that many of those same conservatives bulldozed every relevant norm on the way (especially when they defended the Senate’s refusal to hold a hearing on Merrick Garland’s nomination). Or that they weakened the court’s credibility in doing so. The only thing that matters is that they “won” — and that nothing stands in the way of conservative outcomes.

To be sure, concerns about legitimacy can be overstated. Most cases, even important ones, do not threaten the court’s viability as a forum for resolving pressing disputes.

Yet some issues really do strike at the court’s legitimacy. The challenge to the addition of a citizenship question on the 2020 Census is one of them.

It is difficult to overstate the importance of an accurate census count. Such information plays a key role in the apportionment of political power, the drawing of political districts and the allocation of hundreds of billions of dollars in federal funding. As U.S. District Judge Jesse M. Furman observed: “Even small deviations from an accurate count can have major implications for states, localities, and the people who live in them.”

Every reputable expert — including the Census Bureau’s chief scientist — has found that asking about citizenship will result in a less accurate count. Commerce Secretary Wilbur Ross insisted on adding the citizenship question anyway. His reasons for asking about citizenship are arbitrary and grossly distort the experts’ analysis. There is also devastating evidence that Ross’s stated reasons were false and concealed his true goal of tilting the census count in a manner favorable to Republicans and non-Hispanic whites.

Yet at oral argument, the conservative justices seemed determined to rule for Ross, even if they had to jettison their principles to get there. Usually, the right-leaning justices are hesitant to defer to administrative agencies, look doubtfully upon the Voting Rights Act, refuse to consult international law and will not consider any reasons for agency action beyond the record before them. At argument, these principles went out the window.

Irrational, prejudicial efforts to subvert the census weaken the legitimacy of our constitutional system because they distort the representative nature of our democracy. Upholding such chicanery on grounds that are obviously fictional — and flagrantly at odds with the conservative justices’ stated principles — would raise painful questions about the court as an institution that extend far beyond this case.

Alexander Hamilton famously warned that courts, which lack the power of the purse or the sword, possess “merely judgment.” Nowadays, the court is more important than Hamilton could have ever imagined — and so is the need for good judgment. The institutional legitimacy of the court is itself essential to the rule of law.

The court is not merely a debating society for legal abstractions; nor is it a piñata that conservatives can whack whenever they need a win. It is a branch of government in our constitutional democracy, and its members ought to be concerned with the preservation of that political order. This includes recognizing that the democratically elected branches should in fact be representative of the people — rather than just a means of maximizing the power of one party while minimizing the power of another.

We need courts that transcend partisan warfare to uphold rather than destroy faith in government. The court can play that role. But not if it is seen as a forum in which the game is rigged and half the population is effectively voiceless.

That means adhering to principles even when they lead to unwanted or unexpected outcomes. It means seeing the big picture in deciding where to move the law (and how quickly to do so). And, yes, it means recognizing that the court’s legitimacy is fragile and easily imperiled by decisions allowing one side to manipulate the political process to their partisan, anti-democratic advantage.