Nominating justices to the US supreme court is a responsibility with far-reaching consequences – one of the most potent in a president’s armoury. It will also be one of the first duties of the incoming Trump administration.

The liberal-leaning judge Merrick Garland, President Barack Obama’s nominee for the vacancy left by the death of Antonin Scalia, was denied confirmation hearings by the congressional leadership, so the appointment of a replacement will serve as an early test of president-elect Donald Trump’s conservative credentials.

Facebook Twitter Pinterest The liberal-leaning judge Merrick Garland was denied confirmation hearings by the congressional leadership. Photograph: Evan Vucci/AP

The supreme court is currently split evenly between conservatives and liberals. As part of Trump’s wooing of conservatives, his campaign published a list of 21 potential nominees who would continue the judicial tone of the conservative-leaning Scalia. But a fight is brewing, not least over the role of the court itself.

Faced with 8,000 petitions a year, the full court of nine justices considers around 100 cases a term. With just eight justices currently sitting, several recent judgments have been deadlocked 4-4, including one that blocked Obama’s immigration reform efforts.

Replacing Scalia with a like-minded judge will not shift the complexion markedly, but any further appointments will be of far greater importance. Two of the serving justices are in their 80s and another is in his late 70s, so more appointments are approaching.

While Democrats had been looking forward to a Clinton-directed liberal renaissance of the supreme court, harking back to the civil rights decisions of the mid-1960s, a new period of conservative rulings may now follow.

“All of the people on Trump’s list can be said to be conservative politically,” said Carl Tobias, professor of law at the University of Richmond, “especially on issues like abortion, where he made promises to get the support of the evangelical vote.”

Crucially, the court will now probably hear more cases involving the separation of church and state. The vice president-elect, Mike Pence, made it clear that he wants to see the federal funding of schools with religious orientation. Questions about permitting prayer in public places are also likely to arise.

“Trump may not be overtly religious,” Tobias added, “but there are many, many people who voted for him who believe that’s what he promised to do. Evangelicals were central to his victory and they will surely attempt to hold him to it.”

Mirroring the divisive political climate, the court has found itself increasingly politicised, as seen in several of its most important recent decisions, including last year’s same-sex marriage ruling, the contraception mandate under Obamacare, compulsory union dues, and the overturning in June of a restrictive Texas abortion law.

People who don’t win in legislatures will often try to force an issue on the supreme court – if the judges are willing to hear it. But the sense of judicial impartiality is being eroded because all the liberal justices now sitting were appointed by Democratic presidents and all the conservatives by Republicans.

The justices, particularly Chief Justice John Roberts, have made it clear they resent politicisation, saying the credibility of the court and its rulings are the justices’ chief concern.

“The court doesn’t have the power of the purse or the power of sword, so it has to rely on public confidence or it becomes just another political entity,” said Tobias.

Legal observers are already discussing which cases in the court’s pipeline are likely to disappear as Trump moves to overturn legislation introduced by executive order by Obama. One such issue is a dispute over which toilets in public schools transgender students can use.

A lower court in Virginia this year took guidance from the US education department in ruling for Gavin Grimm, a transgender student, in a case in which the Virginia school board required students to use facilities corresponding to their biological sex, not the gender they identify with. The court may not hear that case if Trump rescinds that order.

With Trump now promising to relax laws governing drilling for oil and gas on public land and to lift other environmental restrictions, challenges before the court could also be dropped.

FLASHPOINTS FOR THE COURT

Donald Trump will be a lucky Potus (President of the United States). Some presidents never get to appoint a supreme court judge, but Trump will be able to choose at least one – a replacement for the late Justice Antonin Scalia, a conservative.

However, with two liberal members on the court possibly eyeing retirement, Trump could also alter the balance of the court so that it is once again a predominantly conservative institution. This could be crucial in determining the outcome of several long-fought battles.

Abortion

A conservative majority would delight the Christian right, which has lobbied hard for a reversal of Roe v Wade, the 1973 ruling that guarantees the right to abortion.

Affirmative action

In June, the court voted to uphold a race-conscious admissions programme at the University of Texas, but this is an issue that will not go away.

Unions

Big business wants the court to overturn a ruling in March upholding the right of public-sector unions to collect fees from workers who choose not to join them.

Church v state

Laws ensuring the separation of church and state could be eroded by a court that agrees there should be greater involvement between religious groups and government.

Gun control

Trump’s unequivocal support for the second amendment suggests that laws restricting the right to bear arms – such as the need for owners to register their weapons – may be overhauled.