The Senate Thursday triggered the so-called "nuclear option" that allowed Republicans to break a Democratic filibuster of Supreme Court nominee Neil Gorsuch.
The chamber is now expected to vote to confirm Gorsuch Friday around 11:30 a.m. ET.
The controversial changes to Senate rules, made along partisan lines, allows filibusters of Supreme Court picks to be broken with only 51 votes rather than 60.
The actions Thursday capped more than a year of tension over an empty Supreme Court seat, with both parties taking action that led to an outcome neither party wanted.
It was a situation loaded with nuance, procedural twists and Senate history -- not to mention a spot on the nation's highest court -- and a standoff that reflected a peak in polarization following a deeply divisive presidential election.
The move came after Democrats blocked the nomination under the previous 60-vote threshold. Only four Democrats -- Sens. Michael Bennet, Joe Donnelly, Heidi Heitkamp and Joe Manchin -- crossed party lines to side with the Republicans.
Subsequent party-line votes allowed the GOP majority to change the precedent for Supreme Court nominees, leading up to the final vote breaking the filibuster.
After the final vote was gaveled, Senate Majority Leader Mitch McConnell went down his row and gave soft high fives to Majority Whip John Cornyn and two aides.
Later on the Senate floor, Democratic Sen. Richard Blumenthal of Connecticut lambasted the high-fives, saying it was not a moment to celebrate. "It saddens me," he said. "No one should sleep well tonight."
McConnell called Gorsuch after the series of votes Thursday to let him know the outcome, according to an aide close to Gorsuch. Members of the White House confirmation team and several former law clerks for Gorsuch watched the vote from the Senate gallery.
When Democrats held the majority, with Sen. Harry Reid as their leader, they used the nuclear option in 2013 to advance lower court and executive branch nominees, much to the disapproval of Republicans.
Now that Republicans are in the majority, they're citing that Democratic action as a precedent.
"Harry Reid decided that executive nominations will be done by simple majority, and we just simply went with the Harry Reid rule today," said Sen. Rand Paul, R-Kentucky. "I don't think this is any different from what he put forward."
Members of both parties acknowledged the risks of the change. It essentially allows the majority party to clear future Supreme Court nominees with ease, so presidents could appoint more ideological nominees that wouldn't require much, if any, bipartisan support.
Manchin described Thursday as a "very sad day," saying the Supreme Court won't have "have a check and balance" system in which the minority has input on future justices. He argued that senators will "rue the day that this happened."
"They all know what goes around comes around," Manchin told reporters. "I was just extremely sad."
Both sides blamed each other for the episode. Democrats blasted Republicans for using the workaround. Republicans, meanwhile, said they felt they had no other option because of the Democratic filibuster.
"For the life of me, I don't understand why the Democrats made such a fuss about this (nominee)," said Sen. Orrin Hatch, R-Utah. "They look stupid. The next one, I mean I expect Armageddon."
Republican Sen. Susan Collins of Maine was heavily involved in bipartisan conversations to find a way to avoid the nuclear option, but she said Wednesday they were simply unsuccessful.
"I've had midnight calls on this, 6:30 a.m. calls on this," she said. "Worked all weekend and we just couldn't get here."
Will the Senate become the House?
With the nuclear option in 2013 affecting executive branch nominees and the one used Thursday affecting the Supreme Court, many senators worry the next casualty to lose the 60-vote filibuster threshold is legislation.
Democratic Sen. Chris Coons, who was also part of bipartisan talks, said on the Senate floor Thursday that he has come to regret voting with his party for the nuclear option nearly four years ago. "And I anticipate that many of my colleagues will come to regret the decisions and actions taken today and tomorrow in this Congress and in Congresses ahead."
Collins said she's going to lead a letter and get signatures from other senators saying they will not support using the nuclear option on bills.
"I think that's the step in the right direction. It's going to take some time to heal," Sen. Mike Rounds, R-South Dakota, said on the idea of a letter. "Clearly emotion is pretty raw in the United States Senate right now."
"We have to be an institution that functions with one another," Sen. Lisa Murkowski, R-Alaska, told reporters. "I do not want the Senate to be the House. It puts it on me and those who also work hard to be bipartisan to be even more bipartisan. So, I'm going to do that and I'm going to start today."
How did this all come about?
On January 31, Trump announced Gorsuch as his pick for the next Supreme Court justice, filling a seat vacated when Antonin Scalia passed away in early 2016.
Gorsuch's first call after being announced went to another judge named Merrick Garland, who'd been nominated by President Barack Obama after Scalia's death. But in the midst of a heated presidential election, Republicans refused to consider Garland's nomination and kept the seat empty until the next president was sworn in.
It was a risky move and Democrats were furious, but it ultimately paid off for Republicans when Trump won in a surprise victory last November.
Fast forward several months, Democrats were still steaming over what some have called a "stolen" Supreme Court seat and brought it up multiple times throughout Gorsuch's confirmation hearings and in Senate floor speeches.
On top of that, Democrats also took issue with Gorsuch's performance at his hearings, saying he was evasive in his answers, and they zeroed in on his decisions in a few cases, painting him as far-right and out-of-the-mainstream.
Republicans, on the other hand, argue Gorsuch answered more than 20 hours of questions and was abiding by what's known as the "Ginsburg standard" so as not to show his cards on how he'd rule in cases that may come before him.
Hitting back against the argument that he's extreme, Republicans say Gorsuch sided with the majority in 99% of his opinions as a federal judge in the past decade, and the GOP said that of the 2,700 cases he has ruled on, 97% were decided unanimously.
Republicans, in fact, felt that Trump picked a relatively safe nominee and rallied behind Gorsuch, even as Democrats signaled early on that they would filibuster his nomination.