Republicans have voted to unilaterally change Senate rules, clearing the way for the confirmation of Donald Trump's Supreme Court pick.
The move to end a Democratic blockade, dubbed the "nuclear option" because it is considered an extreme break with Senate traditions, means conservative judge Neil Gorsuch should be confirmed by Friday.
The battle over the confirmation is significant because if Mr Gorsuch is confirmed it will mean there is a conservative majority among the court's nine justices.
Its ideological leaning could help determine the outcome of cases involving the death penalty, abortion, gun control, environmental regulations, transgender rights, voting rights, immigration, religious liberty and presidential powers.
The upper chamber voted 52-48 along party lines to change its long-standing rules in order to block a procedural tactic called a filibuster against Supreme Court nominees.
It came after Republicans failed by a 55-45 tally to muster the 60-vote super-majority required to end the Democratic filibuster that attempted to deny Mr Gorsuch confirmation to the lifetime post.
The Senate's move means Mr Gorsuch can be confirmed by a simple majority.
"This will be the first and last partisan filibuster of the Supreme Court," Republican Senate Majority Leader Mitch McConnell said on the Senate floor.
He accused Democrats of trying to inflict political damage on President Trump and to keep more conservatives from joining the US' highest court.
But critics of the move said it could lead to a more polarised Senate, court and country.
Senate Democratic leader Chuck Schumer said: "In 20 or 30 or 40 years, we will sadly point to today as a turning point in the history of the Senate and the Supreme Court, a day when we irrevocably moved further away from the principles our founders intended for these institutions: principles of bipartisanship, moderation and consensus."
At 49, Mr Gorsuch would be the youngest Supreme Court appointee for three decades and would replace fellow conservative Antonin Scalia, who died a year ago.
Democrats remain angry that Republicans last year blocked then-president Barack Obama's nominee for the position.
Many refused even to meet Merrick Garland, arguing it was too late in Mr Obama's presidency for him to make an appointment.