Anthony Kennedy has held the key vote on such high-profile issues such as abortion, gay rights, guns, and voting rights.
US President Donald Trump has said he has narrowed his list of Supreme Court justice candidates to five, including two women, with a final decision to be announced on July 9.
The president said on Friday that two candidates could be interviewed as early as this weekend, though he refused to confirm their identity.
“It’s a great group of intellectual talent … they are generally conservative,” Trump told reporters on board Air Force One en route to his private golf club in New Jersey.
The vacancy comes after 81-year-old Justice Anthony Kennedy announced his retirement on Wednesday.
Trump responded to questions about potentional nominees, including federal judges Brett M Kavanaugh and Amy Coney Barrett, as well as US Senator Mike Lee from Utah. He called them all “outstanding”, but did not say if they are on his short list.
The president said he not will push the candidates to say whether they would overturn the 1973 Roe v Wade decision, which established a woman’s right to abortion.
“That’s not a question I’ll be asking,” he said.
Trump’s nominee must win confirmation by the Senate. Republicans control the chamber but only by a slim majority, making the views of moderates, including some Democrats, important.
Trump met senators from both parties at the White House on Thursday to discuss the court vacancy.
Views on abortion were expected to be one that senators will ask the new nominee about in confirmation hearings, even if the president does not.
Kennedy’s replacement could cast a deciding vote on limiting or ending the right to abortion.
“I do not apply ideological litmus tests to nominees, but I want to see integrity, intellect, a respect for precedent and adherence to the rule of law,” moderate Republican Senator Susan Collins told Reuters news agency when asked about Roe v Wade.
Collins, who favours a woman’s right to choose on abortion, joined like-minded Republican Lisa Murkowski at the White House meeting. Also attending were Republican Charles Grassley and Democrats Joe Manchin, Joe Donnelly and Heidi Heitkamp.
Democrat Bill Nelson, asked by reporters if a nominee’s views on Roe v Wade will be important to him, said, “very.”
Senate Republican leader Mitch McConnell said on Friday he hoped the confirmation process would be done “in time for the new justice to begin the fall term of the Supreme Court … the first Monday in October.”
That would put a new justice in place before the congressional midterm elections in November, when all seats in the House of Representatives and a third of those in the Senate will be contested.
While Justice Kennedy was a conservative, he proved to be a somewhat unpredictable “swing” vote over his long career. For example, he sided with the court’s liberals by voting in favour of abortion rights and gay rights in key cases.