Democrats are planning to increase the number of US Supreme Court justices from nine to 13 in an attempt to swing the court away from a heavy conservative majority.
Conservative justices currently outnumber liberals by six to three after former president Donald Trump was able to appoint three justices during his four years in office.
Although the move is expected to draw fierce opposition from Republicans, some Democrats and liberal activists have said all options – including expanding the court – must be considered to prevent the threat to abortion rights, civil rights, gun control and access to healthcare.
A news conference is scheduled for Thursday to announce the introduction of the legislation in both chambers.
It will include representatives from liberal groups including Take Back The Court, which has advocated for the court’s expansion.
President Joe Biden announced last Friday he would form a bipartisan commission to look into potential Supreme Court changes including expansion or imposing term limits instead of the current lifetime appointments.
Congress has the power to change the number of Supreme Court justices, although it has remained at nine since 1869.
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Meanwhile, imposing term limits would likely need a constitutional amendment although some scholars say it could be accomplished by statute.
Last year, Mr Trump was able to controversially appoint his own Supreme Court justice, Amy Coney Barrett, just days before the presidential election following the death of liberal Justice Ruth Bader Ginsburg.
It caused outrage among Democrats as Republicans had previously argued that presidents should not be able to pick a new justice during an election year – and they had managed to get their way.
In 2016, the Senate had refused to consider Barack Obama’s nomination of Merrick Garland to fill a vacancy left by the death of conservative Justice Antonin Scalia.
Instead, the new president Mr Trump was able to fill the vacancy with another conservative justice.