The 'nuclear option' Republicans are using to confirm Supreme Court nominee Neil Gorsuch

— -- Senate Majority Leader Mitch McConnell acted Thursday to change the rules needed to confirm a Supreme Court nominee as Democrats continue their attempts to block Neil Gorsuch from advancing to the position of associate justice.

The move was largely expected as at least 41 Democrats announced their opposition to the nomination, meaning Republicans would be unable to confirm Gorsuch under existing rules, which require 60 votes.

That meant they had no choice other than to -- as has become the popular phrase -- go "nuclear" and reduce the threshold to a simple majority of 51.

President Trump encouraged McConnell to use the option the day after announcing Gorsuch, 49, a Colorado federal appeals court judge, as his first Supreme Court pick.

"If we end up with that gridlock, I would say, if you can, Mitch, go nuclear," Trump said. "Because that would be an absolute shame if a man of this quality was caught in the web."

Here is how the maneuver works:

What is the nuclear option?

"Going nuclear" is a colloquial term that emerged in recent years to describe changing the long-standing precedent for confirmation of presidential nominees. It reduces the minimum required votes from 60 to a simple majority of 51.

Under Senate rules, three-fifths of senators are required to vote in favor of ending debate, or for cloture. But in 2013, Senate Democrats employed a series of procedural maneuvers to change that requirement to a simple majority for all Cabinet-level and judicial nominations, except for those to the Supreme Court.

The elimination of the three-fifths threshold became known as the nuclear option.

While senators have been talking about it for weeks, it became a real option for Supreme Court nominees only on Monday, after 41 of the 48 Senate Democrats and independents caucusing with Democrats announced they would vote against cloture on Gorsuch.

With Senate Republicans holding 52 seats, they need at least eight Democrats or independents to clear the cloture motion. As of Monday afternoon, only four Democrats said they will vote for cloture, and three were undecided.

McConnell expressed certainty that Gorsuch will be confirmed by the end of this week.

"Judge Gorsuch is going to be confirmed. The way in which that occurs is in the hands of the Democratic minority," McConnell said on Fox News on Sunday.

The concern for Republicans, however, is that the next time they are in the minority, Democrats could also use the nuclear option to confirm their preferred nominees, whom Republicans may oppose.

That's exactly what happened after Democrats changed Senate precedent on other nominations to a simple majority in 2013. This year, under those changes, Trump Cabinet nominees largely sailed through on mostly party-line votes.

The move has been traced back to 1957, when then–Vice President Richard Nixon stated the Constitution granted the president of the Senate the authority to override Senate rules by instating new rules upheld by majority vote.

A 2013 paper by Valerie Heitshusen, a legislative branch process expert and an educator in the Congressional Research Service, describes the nuclear option as a "novel" political move that "could undermine the prerogatives exercised heretofore by the Senate minorities or individual senators."

What does the nuclear option do?

The nuclear option would effectively lower the threshold for confirming a Supreme Court justice to 51 votes, from the 60 required to break a Senate filibuster, a tactic to delay a piece of legislation or other Senate process.

In the Senate, at least three-fifths of its members — 60 of the current 100 — are needed to invoke cloture. Using the nuclear option would allow a simple majority of at least 51 to invoke cloture for Supreme Court nominees and move on to a vote on confirmation.

The move was most recently used by Democrats in 2013. Citing an increase in filibustering by Republicans to block then-President Barack Obama's nominees for U.S. appeals court judgeships, the Senate majority leader at the time, Harry Reid, D-Nev., used the nuclear option to create more relaxed Senate procedures for those confirmations. The 60-vote threshold then applied only to confirmation of Supreme Court justices.