A US Senate tactic known as a filibuster has just been used for the first time in half a century to block a Supreme Court nominee.
Democrats rejected Neil Gorsuch’s nomination to the highest court in the land by a 55-45 vote on Thursday.
Republicans retaliated with the so-called nuclear option, changing the rules to ram through confirmation of President Donald Trump’s pick.
The move will leave Congress even more plagued by bickering and deadlock.
Republicans – who control the upper chamber by 52 seats to 48 – fell short of the 60 votes they needed to confirm the Colorado appeals court judge.
His confirmation would preserve a conservative majority on the top court.
Senate Majority Leader Mitch McConnell took steps to respond by overturning the long-standing filibuster tradition for a Supreme Court nominee.
The rule change will enable Mr Gorsuch to be approved by a simple majority in the 100-member chamber.
The controversial “nuclear option” would affect future Supreme Court nominations as well, which some lawmakers say could set a dangerous precedent and erode minority-party rights in the Senate.
“I fear that someday we will regret what we are about to do. In fact, I am confident we will,” said Republican Senator John McCain.
“It is imperative we have a functioning Senate where the rights of the minority are protected regardless of which party is in power at the time.”
Many Democrats say Mr Gorsuch, 49, has shown he favours corporations ahead of workers.
And resentment still simmers over Mr McConnell’s decision last year to deny considering former President Barack Obama’s choice for the high court.
Mr McConnell instead left open the seat to replace the late Supreme Court Justice Antonin Scalia in the hope of filling it with a conservative nominee.
Invoking the “nuclear option” would pave the way for Mr Gorsuch’s final confirmation vote on Friday, allowing him to participate in the last set of cases to go before the Supreme Court this term.
Democrats also used the “nuclear option” in 2013, when they removed filibusters against executive branch and judicial nominees for lower courts in order to ram through then-President Barack Obama’s appointments.
However, they left the filibuster in place for Supreme Court nominees.