Barack Obama has warned US democracy is at risk if Republicans press ahead with plans to fill the Supreme Court seat left vacant by the death of Ruth Bader Ginsburg.
Her death just over six weeks before US election day is likely to trigger a fierce battle over whether President Donald Trump should nominate her replacement at the highest court in America, or if the seat should remain vacant until the result of the race in November against Democratic challenger Joe Biden is known.
In a statement, Mr Obama said: “A basic principle of the law — and of everyday fairness — is that we apply rules with consistency, and not based on what’s convenient or advantageous in the moment. The rule of law, the legitimacy of our courts, the fundamental workings of our democracy all depend on that basic principle.”
Democrats are still seething over the Republican Senate's refusal to act on Mr Obama's Supreme Court nominee, Merrick Garland, in 2016 after conservative Justice Antonin Scalia died 10 months before that election.
Mr McConnell in 2016 said the Senate should not act on a court nominee during an election year, a stance he has since reversed.
Despite that anger, Democrats have little chance of blocking Mr Trump's pick. His fellow Republicans control 53 of the Senate's 100 seats and Mr McConnell, who has made confirmation of Mr Trump's federal judicial nominees a top priority, said the chamber would vote on any Trump nominee.
Even before justice Ginsburg's death, Mr Trump had made public a list of potential nominees.
Conservative activists for years have sought to get enough votes on the Supreme Court to overturn the landmark 1973 Roe v. Wade ruling that legalized abortion nationwide. During the 2016 campaign, Mr Trump promised to appoint justices who would overturn that decision. But the court in July, even with its conservative majority, struck down a restrictive Louisiana abortion law on a 5-4 vote.
The two justices already appointed by Mr Trump were Neil Gorsuch in 2017 and Brett Kavanaugh in 2018. Kavanaugh's confirmation process was particularly heated, as he faced accusations by a California university professor, Christine Blasey Ford, that he had sexually assaulted her in 1982 when the two were high school students in Maryland. Justice Kavanaugh angrily denied those accusations and was narrowly confirmed.
Republicans risk the possibility of liberals embracing more radical proposals should Mr Trump replace justice Ginsburg but Democrats win November's election, with some activists on the left suggesting even before her death that the number of justices on the court should be expanded to counter Trump's appointees.
Confirmation votes could also put more pressure on incumbent Republican senators in highly competitive election races, including Maine's Susan Collins and Arizona's Martha McSally, at a time when Democrats are eying a chance to win control of that chamber. Senator Lisa Murkowski of Alaska also could play a pivotal role.
Many court-watchers expect Mr Trump to attempt to replace Ms Ginsburg with a woman. One possible contender on Trump's list is Amy Coney Barrett, a conservative judge on the Chicago-based 7th U.S. Circuit Court of Appeals who was under consideration in 2018 before Mr Trump picked justice Kavanaugh.
Additional reporting by Reuters. Check out The Independent’s live updates and coverage below: