EARL WARREN was the 20th century’s most consequential American jurist. During his nearly 16-year tenure as chief justice, the Supreme Court ruled, in Brown v Board of Education, that segregation was unlawful; in Gideon v Wainwright, that states must provide attorneys to indigent criminal defendants; in Miranda v Arizona, that police must inform suspects that they have the right to an attorney and to remain silent; and, in Reynolds v Sims, that legislative districts within a state must comprise roughly equal populations. All of those positions today seem uncontroversial; all were furiously contested at the time.

What today seems remarkable, though, is how a liberal justice such as Warren got on to the court in the first place. A Republican president, Dwight Eisenhower, installed him when the Senate was out of session, and though there was some politics in-between (some Southerners worried Warren was too liberal, some liberals that he was too conservative) he was eventually confirmed with a unanimous voice vote in the Republican Senate. What is more, Warren was a Republican himself.

The confirmation hearing for Brett Kavanaugh which began on September 4th went, instead, true to modern form: a pitched partisan brawl played out on live television, with deafening echoes in the more political parts of social media. How did the process of filling one of the court’s nine seats become so contentious?

In the particular case of Mr Kavanaugh, whom President Donald Trump nominated after Anthony Kennedy retired from the bench in June, it is in large part because his appointment will give the court its first solidly conservative majority in generations. In a court with four mostly liberal justices and four pretty solid conservatives, Mr Kennedy had sided sometimes with one bloc, sometimes with the other: he was the court’s swing vote. Mr Kavanaugh will be far more reliably conservative.

The excitement and controversy over Mr Kavanaugh also had to do with Mr Trump himself. He has been implicated in a conspiracy to break federal law and is under investigation for his campaign’s ties to Russia. The court may have to decide whether Mr Trump can be forced to testify in that investigation, or whether he can be indicted, or whether he can pardon himself. Mr Kavanaugh’s views on the powers of the presidency may determine how the court rules on such questions.

Beyond the particulars of Mr Kavanaugh’s appointment, though, the political drama that now surrounds the Supreme Court is explained by the fact that over the past four decades it has decided some of the most inflammatory and divisive issues in America: Can gay people get married? Can universities consider race in admissions? Should abortion be legal? It also makes decisions with far-reaching political implications: What limits can be set on gerrymandering? Does contributing money to political candidates count as speech? Most weightily, in Bush v Gore: Who gets to be president?

Such a range of questions comes before the court partly because it fills an unusual role. It interprets the constitution as well as statutory and administrative law. Many other countries divide those duties, with a constitutional court handling one type of case and a supreme legal court handling questions of law. America, like India and Japan, invests both in a single body.

But a bigger reason is that, over recent decades, Congress has become both more partisan and more prone to gridlock. Questions that might otherwise be settled legislatively are instead the object of arcane legal and constitutional wrangling. As the court’s role has grown more political, so has the choice of its judges, which the constitution vests in the president. The days when Republican presidents nominated liberals like John Paul Stevens, David Souter, Harry Blackmun and William Brennan, or Democrats appointed conservatives like Byron White, are long gone. Since the 1980s, presidents have picked justices they think will consistently stay on their side of the partisan divide, and they have been largely successful (see chart).

Because justices serve for life, the battle over Mr Kavanaugh, who is 53, is a battle over the country’s direction for decades to come. And it is one the Republicans will all but certainly win. Because filibusters can no longer be used for confirmations, it only takes 51 Senate votes to approve a nominee. There are 51 Republicans in the Senate. And even senators who are retiring, and sometimes critical of Mr Trump, can be relied on to vote for his pick on this matter.

But if the Republicans’ victory in this battle is politics as usual, their overall victory in the war for a Supreme Court majority sits on far more dubious ground. After Antonin Scalia died in February 2016, Barack Obama nominated a moderately liberal judge, Merrick Garland, to take his place. But Mitch McConnell, the Republican senate majority leader, refused to hold confirmation hearings for him, a move without modern precedent. Mr Garland’s nomination lapsed when Mr Obama’s presidency ended in January 2017; Mr Trump nominated Neil Gorsuch, a conservative jurist, to the seat instead, and Mr McConnell’s Senate promptly confirmed him. This stolen seat will, if Mr Kavanaugh is confirmed, form part of the new conservative majority.

Mr McConnell knew what he was about. As the chart shows, although Mr Garland is not particularly liberal, if he had replaced Scalia, who was staunchly and brilliantly conservative, the court would have moved more sharply to the left than it has for decades. Mr Trump also knew what he was about. Having a Supreme Court seat held empty for him gave him an opportunity to appeal to conservative voters by making it clear that he would fill it with someone of whom they would approve. Even if you dislike me, he told a rally in July 2016, “you have to vote for me anyway. You know why? Supreme Court judges. Have no choice.” The gambit worked.

The guarantee of a conservative justice mattered to white evangelicals—who might otherwise have had problems with a foul-mouthed, thrice-married libertine—because of Roe v Wade, the 1973 ruling that recognised a constitutional right to abortion. Conservative Christians were scandalised at such a decision being taken by the Supreme Court; it was this issue above all others that brought such voters to the Republican party, and this issue above all others that politicised the court.

In 1992 Planned Parenthood v Casey provided an opportunity for the court to overturn Roe. The court did not take it, but its ruling in the case did allow states to pass new restrictions and regulations on abortion provided that they did not impose an “undue burden” on women seeking abortions. The result is a game of Grandmother’s Footsteps; states impose rules on abortion clinics—such as requiring their doctors to have admitting rights at local hospitals, or demanding that their corridors be widened—that do as much as possible to make them close down without imposing what the court would see as an undue burden on their clients.

It is by upholding such restrictions, rather than overturning Roe, that a conservative court is likely to reduce abortion rights. The court is typically reluctant to stray too far from public opinion, and most Americans do not want Roe overturned. Mr Kavanaugh, for his part, has called Roe “settled law”, which lends credence to the idea that whittling away is the likely approach. (That said, he has also noted that the court “can always overrule its precedent”—as it did in a liberal direction in Lawrence v Texas, invalidating laws banning sodomy.)

But the piecemeal approach to abortion rights could still see tens of millions of women in states with conservative legislatures denied the ability to exercise in practice the right Roe recognised in principle. Mr Kennedy acted as a stay in such matters. Mr Kavanaugh probably will not. One of his former clerks wrote in July that “on the vital issues of protecting religious liberty and enforcing restrictions on abortion, no court-of-appeals judge...has a stronger, more consistent record” than he does.

In the only major abortion case he heard during his 12 years on the US Court of Appeals for the DC Circuit, Mr Kavanaugh dissented from a ruling that allowed an undocumented teenager in custody to obtain an abortion, arguing that forcing the girl to wait a couple of weeks was not an undue burden. This ruling worries liberals, though it was also criticised at the time by conservatives who thought it did not go far enough.

Mr Kavanaugh’s expansive view of religious liberty also has gay-rights activists worried. Mr Kennedy’s landmark ruling recognising the right to same-sex marriage is unlikely to be overturned; there is no public appetite for the mass annulment of same-sex marriages. But in this, too, the court’s new conservative bloc might seek to limit that right in practice by means of incremental exemptions—for instance, permitting clerks with religious objections to deny gay couples marriage licences.

On various racially charged issues things may be sharper. Scalia and the court’s three still-sitting conservatives all ruled against affirmative-action policies. Mr Kennedy, though, unenthusiastically joined the court’s liberal wing in upholding universities’ rights to consider race in admissions. Mr Kavanaugh and Mr Gorsuch (untested, as yet, on this matter in the court) seem more likely to side with the other three conservatives. Mr Kavanaugh worked on the George W. Bush administration’s opposition to the University of Michigan Law School’s affirmative-action policy. He also wrote an op-ed while in private practice approvingly citing Scalia’s belief that “in the eyes of government, we are just one race here. It is American.” The court has, for the most part, also recently permitted states to enact voter-ID laws that opponents say are intended to depress minority turnout. Mr Kavanaugh is unlikely to change that.

Another worry about the new court is that it may be too deferential to executive power. Mr Kavanaugh, who spent years working for the independent counsel’s team that investigated Bill Clinton in the mid 1990s, later decided such investigations impinged unreasonably on a president’s time and attention. During a panel discussion in 1998 he indicated that the law protects a sitting president from indictment. In a 2009 law-review article, he proposed that Congress pass a law protecting presidents from criminal investigations and civil suits while they were in office.

Mr Kavanaugh does not believe presidents are above the law: the article suggested temporary investigatory deferrals, not permanent immunity. But during his confirmation hearing Mr Kavanaugh refused to answer any specific questions on such matters, including whether presidents can pardon themselves.

On more general matters of judicial philosophy he was, for what it was worth, more forthcoming. When he interprets the constitution, Mr Kavanaugh told the judiciary committee, he considers himself bound by the document’s “original public meaning, of course informed by history and tradition and precedent.” This view, that the constitution has one meaning, the one it was originally taken as having by its readers, and that singular meaning is best found by close study of the text, is known as originalism. Scalia was for a long time its most prominent exponent on the court (its most ardent advocate now is Clarence Thomas). Partly because Scalia regularly and persuasively expounded on its merits it has gained much currency. This is particularly true on the right—Mr Thomas is the court’s most conservative justice—but holds to some extent across the ideological spectrum. Justices pay far more heed to specific wordings today than they did in the Warren Court’s heyday. As Elena Kagan once put it, “We’re all textualists now.”

Associate justice, no peace

However some, such as Eric Segall of Georgia State University, the author of a forthcoming book on originalism, worry that originalist language is often used by justices to uphold positions quite at odds with the philosophy’s seemingly hands-off tenets. “Justices use the rhetoric of originalism to mask political judgment,” Mr Segall says. Past proponents of originalism argued that courts should strike down laws only in the case of clear textual error. Today, argues Mr Segall, proponents of originalism want to “shrink the federal government and deregulate the economy, but there is no reasonable originalist argument for that kind of strong judicial interference with our political system.”

Reasonableness of argument notwithstanding, such an agenda may well come to dominate the court in the years and decades to come. It would not be the first time. In the early 20th century the court repeatedly struck down minimum-wage laws and limits on hours worked, which it believed illegally infringed on “liberty of contract” guaranteed by the 14th amendment’s due-process clause. Under this theory, the court invalidated several of Franklin Roosevelt’s New Deal laws.

It reversed course at roughly the same time that Roosevelt threatened to dilute the justices’ power by expanding the bench (since 1869, the court has had nine justices, but this is convention: the constitution says nothing about its size). “It is difficult to see,” Owen Roberts, a justice who changed course, later wrote, “how the court could have resisted the popular urge for uniform standards throughout the country—for what in effect was a unified economy.” As if chastened, the court returned to a more restrained role for decades. It cut loose again, in the opposite direction, only with the advent of the activist Warren court.

Some hope Chief Justice Roberts will tack leftward, as his namesake did (and, indeed, as justices tend to, over time, whatever their original ideological stance, though the trend is hardly universal). With Mr Kennedy gone, it will now be Mr Roberts who has four justices to his left and four to his right. Though he is without doubt a man of the right, he also evinces caution and a sense of constitutional propriety. He voted twice with the court’s liberal bloc to uphold Mr Obama’s Affordable Care Act, in part, perhaps, because he felt that the court should not throw out a major piece of legislation for which the president had a clear mandate.

But Mr Roberts may not be the median judge for long. Two of the court’s liberals are in their eighties; if one dies, or is forced by ill health to retire, before the next election, and Mr Trump were to fill the void, the median position might well move rightward to Mr Gorsuch, hardening the court’s ideological tenor.

That prospect may well make the bad situation brought about by the stonewalling of Mr Garland worse. Brian Fallon, chief spokesman for Hillary Clinton’s presidential campaign in 2016, recently started Demand Justice, a court-focused pressure group. He wants his party to be as ruthless and court-focused as the Republicans have been. Democrats, he says, need to “get over the idea that the courts are anything other than a place where a power struggle is taking place.” If another seat does come up soon, and if the Democrats retake the Senate in this year’s elections, they will probably stonewall Mr Trump’s nominee, just as Mr McConnell did Mr Obama’s.

In the face of growing political rancour, calls for reform are getting louder. Perhaps the most widely canvassed idea is that justices should serve a single 18-year term rather than for life, with two new justices chosen each presidential term. Daniel Epps and Ganesh Sitaraman, of Washington and Vanderbilt universities, have proposed more sweeping reforms. The nine permanent justices could be replaced with nine-judge panels drawn at random from the entire federal appellate bench, comprising around 180 judges, to sit for two-week periods. Alternatively, the court could be expanded to 15, with five justices chosen by Republicans, five by Democrats and the last five by the justices themselves, who would have to nominate them from the appellate bench unanimously.

Either reform could reduce the role of partisanship in judicial selection. But they could also simply push partisanship downward and turn every federal appellate nomination into the sort of brawl seen over the past weeks. And enacting them would require both parties to cede power over the courts, which they will never want to do at the same time.

But doing nothing carries its own risks. With ample justification, Democrats want revenge for the theft of Mr Garland’s seat, and how it paved the way for Mr Trump’s ascent to the White House. Faced with a conservative court that could frustrate their ambitions for decades, some have begun whispering about court packing—adding justices to the court should they retake Congress and the White House. No doubt that will outrage Republicans, and lead them to do the same the next time power swings back. Both sides will prize ideological purity over competence and independence of mind.

Down this path lies the dark day when another part of the government takes the decisive, perhaps irretrievable, step of ignoring a Supreme Court ruling. And at that point the constitution’s checks and balances come tumbling down.