When Justice Antonin Scalia died in early 2016, liberals and conservatives alike agreed that the next justice could transform American life for a generation or more. Donald Trump warned that if Hillary Clinton got to make the appointment “our country is going to be Venezuela.” Mrs. Clinton responded that a Trump justice “would threaten the future of our planet.” The partisan forecasts are even more ominous as Senate hearings begin next week on Mr. Trump’s nomination of Brett Kavanaugh to succeed Anthony M. Kennedy on the Supreme Court.

A single judicial seat should not be so freighted. And it might not be, if the court weren’t so willing to insert itself in disputes that ought to be resolved by the political process. We’re a long way from the notion of judicial restraint described by Justice Louis Brandeis a century ago. “The most important thing we do,” he said, “is not doing.

We may pride ourselves that we have self-government, but for decades we’ve turned to the court to settle our most difficult social and political issues: abortion and gay marriage, campaign finance and gun control, even a disputed presidential election. When the justices rule the way we like, we laud them for “interpreting” the Constitution. When they don’t, we complain they’re “making the law” based on their own predilections. A good justice is an umpire; a bad justice is a player. No real principle seems to be involved in our assessments of the court, only whether we endorse the outcome of this case or that one. The court has become just another political prize to be won by the party in power, not the neutral arbiter this country’s founders envisioned.

“We need more Republicans in 2018 and must ALWAYS hold the Supreme Court!” President Trump tweeted this past spring. That kind of cynicism corrodes any legitimacy the court has left.

The justices have been complicit in this, all too happy to intervene — for instance, in Roe v. Wade in 1973, Bush v. Gore in 2000 and Citizens United in 2010. The court would have us believe it’s only a bystander, but the reality is that the justices have virtually total control over which cases they hear. Too many times the court steps into the fray purely because it can. Just as bad, when the justices should get involved — not to pick winners and losers in ideological battles, but to correct structural flaws in the electoral process or to protect minority rights — they often shrink from their duty. The cases on partisan gerrymandering that the court ducked in June, for example, were precisely the type it ought to be resolving.

The court’s arrogance enfeebles Congress. Lawmakers recognize there’s little benefit in doing their jobs if, in the end, the court is going to resolve the hard questions anyway. This is why many reformers and activists focus on the court. Witness the money and energy expended on litigating, say, abortion. When demonstrators convene outside the Supreme Court, they surely miss the irony that they’re marching right past the Capitol across the street.

Under Chief Justice John G. Roberts Jr., we have a court of blue chambers and red chambers. It wasn’t always that way. In the past, presidents weren’t driven solely by hyperpartisan agendas for the court, in part because the court wasn’t in the maelstrom of so many divisive issues as it is today. Yes, justices sometimes disappointed the presidents who appointed them — like Earl Warren, selected by Dwight D. Eisenhower to be chief in 1953, and David H. Souter, picked by George H.W. Bush in 1990.

But now, thanks to more cynical vetting, nominees act on the bench the way the presidents who chose them expected. Barack Obama got what he wanted with Elena Kagan and Sonia Sotomayor. So, too, in most votes, did George W. Bush with John Roberts and Samuel A. Alito Jr., and Bill Clinton with Ruth Bader Ginsburg and Stephen G. Breyer.

When the votes in contentious cases can be predicted at the outset, constitutional law simply becomes partisan politics by another name. If you typically know beforehand how justices will vote based on which president appointed them, then what’s the point of having a court that, in theory, operates above politics?

Of course, the court sometimes must act decisively to protect rights. By design, the unelected, largely unaccountable Supreme Court serves as a bulwark against tyrannical majorities. The First Amendment’s guarantee of free expression envisions the protection of repugnant views. And few legislators are apt to defend the rights of criminal suspects. That’s why there are constitutional prohibitions against unreasonable searches and against self-incrimination. The court’s role is to vindicate these unpopular protections. In one of its finest moments, in Brown v. Board of Education, the court gave force to the 14th Amendment’s guarantee of equal protection for all.

Once upon a time, liberals looked to the Supreme Court to secure social justice, while conservatives abhorred what they called judicial activism. Now that conservatives are on the verge of locking down control of the court, they can’t wait for the court to enshrine new legal doctrine to achieve victories that have eluded them in the political branches, or, if need be, to validate successes won now that the White House and Congress are in Republican hands. Rollbacks of federal regulation of the environment, the workplace, health care and the voting booth are the constitutional grail for conservatives. Suddenly, liberals are the ones preaching judicial restraint. In the fight for the court, hypocrisy is king.

A month before the Constitution was ratified in 1788, Alexander Hamilton explained what he saw as the source of power for the new Supreme Court. The other branches, as well as the populace, would obey the justices because of their prestige. Their rulings would be based “neither on force nor will, but merely judgment.” By Hamilton’s reckoning, while the president “holds the sword” and Congress “commands the purse,” the court would be “the least dangerous branch.”

That’s no longer so. Yes, the president can initiate war. And Congress, beholden to special interests, can pass foolish laws or do nothing at all. But the court’s self-aggrandizement in recent decades is more insidious and destructive of American values in the long term. With deep distrust in our elected representatives, we have come to believe democracy is broken. Too often we’ve hoped that the justices will be our saviors. With so much dysfunction in government, the justices see themselves that way, too. But even in the current age, we need to demand more from the political branches of our government. We do not need, nor should we want, the court to save us from ourselves.