Joe Biden has accused Donald Trump of an “abuse of power” over his plans to replace the late Supreme Court Justice Ruth Bader Ginsburg before the presidential election.
Mr Trump has said he will nominate a woman next week to fill the seat of the liberal justice and women’s rights champion in the country’s highest court.
The 87-year-old had sat on the Supreme Court since 1993 until her death on Friday due to complications from pancreatic cancer.
Her death has sparked a battle over how a successor will be appointed.
Mr Biden urged Senate Republicans to delay any vote on her replacement until after the November election.
Speaking in Philadelphia, the Democratic presidential candidate said: “Voters of this country should be heard … they’re the ones who this Constitution envisions should decide who has the power to make this appointment.
“To jam this nomination through the Senate is just an exercise of raw political power.”
The presidential hopeful also reiterated his pledge to nominate an African-American woman to the court, which would be a historic first, if he wins the race to the White House.
The procedure for appointing a Supreme Court justice allows the president to nominate a candidate and then requires the Senate to confirm them.
This would give Mr Trump the opportunity to expand the court’s conservative majority to 6-3.
Democrats have pointed to the Republican Senate’s refusal in 2016 to act on then president Barack Obama’s Supreme Court nominee.
Conservative Antonin Scalia had died 10 months before that year’s election, and Senate majority leader Mitch McConnell then said the Senate should not act on a nominee during an election year.
This time, he has reversed his stance.
It would take four Republicans to break ranks to keep Mr Trump’s nominee off the court.
So far two of the 53 Republicans in the 100-seat chamber – senators Lisa Murkowski of Alaska and Susan Collins of Maine – have said they oppose moving ahead swiftly with plans for a nomination, confirmation hearings and votes before the presidential election.
Two conservative women have been named as potential candidates: Amy Coney Barrett of the Chicago-based 7th Circuit, and Barbara Lagoa of the Atlanta-based 11th Circuit.
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Ms Barrett is a devout Roman Catholic who abortion rights groups say would be likely to vote to overturn the landmark decision that legalised abortion nationwide.
Ms Lagoa was the first Latina on the Florida Supreme Court and would become the youngest justice on the Supreme Court if appointed at 52 years old.
Mr Trump has already appointed two justices: Neil Gorsuch in 2017 and Brett Kavanaugh in 2018.