By Cass Sunstein

Bloomberg News

These are not the best of times for the U.S. Supreme Court. But whether or not Judge Brett Kavanaugh is ultimately confirmed, and despite the intense heat of the moment, the court’s fundamental legitimacy need not be, and should not be, put in question.

For well over 200 years, the Supreme Court has helped commit the nation to the supremacy of law. That commitment is a precious achievement. It safeguards liberty, and it holds off authoritarianism.

It unifies Republicans and Democrats. It brings together judges appointed by such diverse presidents as Ronald Reagan, Bill Clinton, Barack Obama and Donald Trump.

In thinking about the Supreme Court, we tend to focus on largest constitutional questions, which can split people, and judges, along partisan lines — affirmative action, campaign finance, abortion, same-sex marriage. But most of the work of federal judges, and of the Supreme Court itself, never reaches the front pages.

The question might be whether the Occupational Safety and Health Administration has the legal authority to reduce workers’ exposure to silica in the construction industry; whether the Environmental Protection Agency has complied with the Administrative Procedure Act in issuing a new rule to govern methane emissions; whether it is arbitrary, and therefore unlawful, for the Securities and Exchange Commission to refuse to engage in quantitative cost-benefit analysis before imposing disclosure requirements on the private sector.

These are technical issues, to be sure. But they are exceedingly important. In resolving them, federal judges require officials to adhere to the law as enacted by Congress.

Most of the time, such judges agree on the proper resolution of legal questions, regardless of whether they were appointed by a Republican or Democratic president. On the all-important courts of appeals, Republican and Democratic appointees tend to be in accord on what the law requires — even if that means that they must rule against executive branch officials who are working for a president of their preferred political party.

Even on the Supreme Court, which deals with the hardest questions, there is far more agreement than one might think.

In the most recent term, for example, Chief Justice John Roberts, appointed by a Republican, voted with Justice Elena Kagan, appointed by a Democrat, no less than 80 percent of the time. Justice Stephen Breyer, known as liberal, voted with Justice Samuel Alito, known as conservative, 60 percent of the time.

Indeed, Justice Clarence Thomas, unquestionably the most conservative member of the court, voted with Justice Sonia Sotomayor, often described as the most liberal, half of the time.

All recent presidents, Democratic and Republican, have been frustrated to find that the law often forbids them to go in their preferred directions — whether the issue involves infrastructure, climate change, immigration or criminal justice.

In major cases, recent presidents, including Obama and Trump, have lost in court. Even more important, they know that courts will not allow them to do whatever they want. Most of the time, that is a crucial deterrent to decisions on the part of the executive branch that would violate legal restrictions.

It’s true of course that recent events —the controversy over Kavanaugh and the sharp partisan disagreement about whether he should be confirmed —are going to create a real test for the court’s legitimacy. The justices are entering an unusually difficult period.

If Kavanaugh is confirmed, many millions of Americans will conclude that something terrible has been done —through an exercise of raw political power. Whether or not they are right, that widespread belief will cast a new cloud over the court.

Kavanaugh — or for that matter any Trump-appointed justice —would give the court a solid conservative majority, with the votes to move the law in dramatic new directions. With respect to sex equality, affirmative action, voting rights, access to court, commercial speech, and abortion, the nation could be in for a wild ride, in which 5-to-4 majorities consistently end up ruling that the meaning of the Constitution looks a lot like the political convictions of the Republican Party.

That would be ugly and dangerous. Let’s hope it never happens.

Chief Justice Roberts has shown a keen interest in narrow, humble rulings, able to unify judges who disagree on the deepest questions. Now in particular, the chief justice has both an opportunity and an obligation to ensure incremental movements in the law — to increase the likelihood that in a period of profound political division and distrust, the court is not speaking for a political party.

In short: As much as any time in American history, this is a period for judicial minimalism, in the form of rulings that can attract support from Americans with diverse commitments — as well as the appointees of both Republican and Democratic presidents.

Cass R. Sunstein is a Bloomberg Opinion columnist. He is the author of “The Cost-Benefit Revolution” and co-author of “Nudge: Improving Decisions About Health, Wealth and Happiness.”