News of the death of supreme court justice Antonin Scalia had barely started making smartphones buzz with alerts on a quiet holiday weekend before one Senate staffer vocalised what all of Washington was already wondering.



Supreme court justice Antonin Scalia dies at 79 Read more

“What is less than zero?” asked the communications director for Utah Republican Mike Lee on Twitter. “The chances of Obama successfully appointing a supreme court justice to replace Scalia?”

It might seem shocking that the political classes were already speculating how much opposition Congress will put in the way of the president’s replacement, before news of a 79-year-old man’s death had even been officially confirmed.



Yet if there is anything that will test to destruction what little bipartisan spirit is left in US politics, it is a vacancy on the supreme court bench in the final few months of a presidency loathed by many of the very senators who have to ratify a new appointment – with a minimum of 60 votes.



The prospect of several likely vacancies in the next few years – Scalia was one of four of the nine justices over 75 years old – had become a central feature of the rancorous election battle to replace Obama.



Whether liberal or conservative, the next president will have a once-in-a-lifetime opportunity to remake the precariously balanced supreme court in their image.



This bench, on which Scalia was the fifth and most conservative justice appointed by a Republican president, enraged the right by legalising same-sex marriage and Obamacare, but appalled the left by repealing voter protections from the civil rights era and allowing unlimited campaign donations which have created a free-for-all in election funding.



Over the next few months, the court faces even bigger tests of Obama’s legacy in the shape of legal challenges to his immigration reform and action on climate change.



The court has suspended executive actions in both areas, pending appeal, but allowing the remaining eight judges to go ahead and rule without Scalia risks a four-four split, or the possibility that unpredictable conservative Anthony Kennedy might side with liberals and give Obama two historic victories.



The Republicans who control the Senate may well be tempted to stall for time, or face no choice but to do so until, they hope, the 2016 election goes their way and a Republican president is sworn in next January.



Republican presidential candidates Donald Trump and Marco Rubio issued messages of condolence on Saturday, before the normally speedy White House even had a chance to acknowledge Scalia’s death.



But waiting 11 months is a risky proposition for the Senate majority leader, Mitch McConnell, who will be under fierce pressure to meet Obama halfway on a moderate replacement long before then. However, within two hours of the news of Scalia’s death, McConnell had said publicly: “The American people should have a voice in the selection of their next supreme court justice. Therefore, this vacancy should not be filled until we have a new president.”



Facebook Twitter Pinterest The Senate majority leader, Mitch McConnell. Photograph: Michael Reynolds/EPA

Antonin Scalia's death calls supreme court gun rights stance into question Read more

There are risks for Senate Republicans in delaying. Not only are the current leading GOP candidates – Trump and Ted Cruz – almost as estranged from their party colleagues on Capitol Hill as opponents like Hillary Clinton or Bernie Sanders would be, there is also the chance that Democrats could take back control of the Senate in November and have the power to force through a figure light years away from Scalia.

When Democrats last had control of the Senate, in Obama’s first term, the president was able to appoint Sonia Sotomayor, the first Latina on the bench and an even more ardent defender of liberal principles than justice Ruth Bader Ginsburg.

The 10-week battle over that appointment still resonates, however: the New Jersey governor, Chris Christie, is vilified by today’s more conservative Republican party for voicing support for the appointment.



A year later, with midterms looming, Obama appointed Elena Kagan, a somewhat milder liberal, with the help of five Republican senators who broke with their party.



To pull off this feat a third time, especially now Republicans control a majority in the Senate and there are precious few willing to cross the aisle in either direction, could be the final and stiffest test of the Obama presidency.

