If confirmed, Brett Kavanaugh, President Donald Trump’s pick, will restore a conservative majority at the country’s highest court.
For experts, the polarisation at the court reflects the partisan divisions of society. And given the current term rules, the differences, they say, are likely to stay.
In the US, the nine-member Supreme Court is the third branch of the federal government and is often the final word on highly contentious laws, disputes between states and the federal government, and final appeals to stay executions.
Nominations are made by the president and have to be approved by the Senate in usually very tense hearings.
Candidates do not have to meet any qualifications.
Divisions at the top court are not new but, for the first time in its history, ideological positions coincide with party lines, Prof Neal Devins and Prof Lawrence Baum wrote in the study How Party Polarization Turned the Supreme Court into a Partisan Court.
Since 2010, all of the members appointed by Democrats are liberal while all its Republicans are conservative.
“Today’s partisan split, while unprecedented, is likely enduring,” they said, pointing to a “growing ideological distance” between the two groups and the lack of centrists among them.
The partial exception, they added, was Justice Anthony Kennedy, a Republican appointee who was the court’s swing vote and is now being replaced following his retirement.
Observers say votes by justices in recent years, for example, have mirrored the positions of the parties of the presidents who appointed them. Key cases have been decided on 5-4 votes.
“It becomes increasingly difficult to contend with a straight face that constitutional law is not simply politics by other means,” University of Chicago Law Professor Justin Driver said, “and that justices are not merely politicians clad in fine robes.”
In the UK, the 12-member Supreme Court was created in 2009, replacing the Law Lords in Parliament. It acts as a final court of appeal in cases of major public importance.
The justices are nominated by an independent commission, chaired by the president of the court, a senior judge from anywhere in the UK to be named by the president and members of the appointment commissions from England and Wales, Scotland and Northern Ireland. A number of senior judges must be consulted by the commission before any decision is taken.
Candidates must have been a senior judge for at least two years or a qualified lawyer for at least 15 years. When someone is chosen, the decision is sent to the justice secretary, who can accept or reject it. If accepted, the name is then sent to the prime minister, who recommends it to the Queen, who makes the appointment.
Unlike the UK, the candidates for the US Supreme Court have to be confirmed by the Senate.
For many, Mr Kavanaugh’s nomination has been the most contentious in recent history.
“We have gone from routinely having supermajorities for nominees in both parties to narrow-to-almost-party-line votes for Supreme Court justices,” Michael Waldman, president of the nonpartisan Brennan Center, told PBS.
In March 2017, Neil Gorsuch, President Trump’s first Supreme Court nomination, was confirmed by a 54-45 vote. The confirmation of Mr Kavanaugh, who already faced resistance from Democrats, has been engulfed by allegations of sexual misconduct that he denies.
The process, often described by experts and the media as “broken”, is unlikely to change, at least for now.
In the US, there are no term limits for justices. Lifetime appointments were originally designed to isolate them from political pressure but, given the current climate, critics argue that, in fact, the opposite is happening and have defended the introduction of fixed terms.
As the court’s decisions, from gay marriage to abortion, have a profound impact on society, presidents have some influence on policies for a long time after leaving office. And members nominated at a relatively young age – Clarence Thomas was 43 when he was appointed in 1991 – can serve for several decades.
Take Mr Kavanaugh. If confirmed, he is expected to push the court to the right on a number of issues. Being 53 years old, he is likely to be there for many years.
On the other hand, those who oppose term limits say this could actually make the politicisation even worse, as presidents would be more inclined to make partisan nominations given the temporary terms.
In the UK, there is no limit to justices’ terms but they must retire at the age of 75. Similar age limits are in place in other Western European countries – in Germany, they serve 12-year terms with no re-election allowed and must retire at the age of 68 – and in Canada and Australia, for example.