Republicans have secured the numbers needed to ensure that President Donald Trump’s Supreme Court nominee will face a confirmation vote in the Senate.
Senator Mitt Romney of Utah has given the party the 51 backers needed to move forward with voting on Mr Trump’s candidate to replace Ruth Bader Ginsburg, who died on Friday.
Democrats argued there should be no confirmation in an election year.
The move guarantees a bitter political battle going into November’s vote.
President Trump says he will announce his chosen nominee on Saturday.
Supreme Court justices are nominated to the bench by the US president, but must be approved by the Senate.
With the death of Justice Ginsburg, a liberal stalwart, Mr Trump has been given the chance to cement a rightward ideological tilt of the nine-member court by replacing her with a conservative.
Senate majority leader Mitch McConnell has vowed to hold a confirmation vote before the election in November, but a question mark had hung all week over whether enough Republicans in the chamber would back him.
Although they hold a slim majority with 53 seats, two centrist Republican senators - Susan Collins of Maine and Lisa Murkowski of Alaska - said they were sceptical of confirming a lifetime judicial appointment in an election year.
Mr Romney, a Trump critic who Mr Trump called “our worst senator” earlier this month, was seen as a possible defector.
However, in a statement released on Tuesday, Mr Romney said he would give Mr Trump’s nominee a hearing, citing “historical precedent”.
“My decision regarding a Supreme Court nomination is not the result of a subjective test of ‘fairness’ which, like beauty, is in the eye of the beholder,” he said.
“It is based on the immutable fairness of following the law, which in this case is the Constitution and precedent. The historical precedent of election year nominations is that the Senate generally does not confirm an opposing party’s nominee but does confirm a nominee of its own.”
Republicans fall into line
It didn’t take long for Republican senators to fall into line.
In the end, concerns about hypocrisy - just four years ago the Republican majority blocked Barack Obama’s Supreme Court nomination because it was made in “an election year” - took a backseat to simple power politics. The Republicans have the opportunity to cement a solid conservative majority on the high court, and they won’t let it slip away - even if there are political consequences for Republican senators seeking re-election in moderate states.
Democrats will howl with anger, but at this point there’s not much they can do, procedurally, to stop what seems inevitable. Instead, they will issue warnings of grave consequences if and when they take power next year. They’ve threatened to add seats to the Supreme Court, admit new, Democratic-leaning states (namely, Washington DC and Puerto Rico) or strengthen the power of the Senate majority. All those are hypothetical battles for another day, however.
For the moment, the Republicans are relishing the prospect of the biggest swing in the ideological makeup of the court in three decades - with issues like abortion, voting rights, healthcare, gun control and civil liberties hanging in the balance.