With the unexpected death of United States Supreme Court Justice Antonin Scalia this weekend, the political battle lines have been drawn. President Obama has made clear that he plans to nominate a successor. His opposition is equally adamant that he should not do so, but allow the choice to be made by the next president.

Many Republicans, including presidential hopefuls and current Senators Marco Rubio and Ted Cruz, have already announced their intentions not to act on any nominee the president sends them.

“The president can nominate whoever he wants,” Rubio told Fox News. “We’re not moving forward on it, period.”

The Supreme Court was to rule on many controversial issues this year, including abortion, immigration, affirmative action and voting rights. And because many of the court’s decisions have been decided by a 5-4 vote, typically with the four liberal justices on one side and the five conservative justices on the other, both parties are well aware that replacing Justice Scalia with a more liberal justice will change the balance of power on the court.

Leaving Justice Scalia’s seat empty until there is a new president would mean that difficult cases this term could come down to a tie, evenly split along ideological lines. In those cases, the lower courts’ decisions would stand, as if the Supreme Court had never considered them. This would definitely impair the court’s responsibility to “say what the law is.”

So what will it take to get a new justice named?

Step 1: The presidential pick

The first thing to know is that the Constitution of the United States gives the power of nomination to the president.

Article II, section 2 provides that the president “shall nominate, and by and with the advice and consent of the Senate, shall appoint … judges of the Supreme Court.”

By law, President Obama can nominate whomever he wants to replace Justice Scalia. Appointment is really a three-step process: nomination (by the president), confirmation (by the Senate), and appointment (by the president again).

It’s somewhere between nomination and confirmation that the going gets tricky.

Step 2: The Senate Judiciary Committee

Once the president has made a choice, the nomination is referred to the United States Senate. Since the early 19th century, this has meant that the nomination will first be considered by a smaller group within the Senate, the Senate Judiciary Committee.

The Judiciary Committee currently has 20 members – 11 Republicans and 9 Democrats – and has a three-step process of its own.

First, it conducts a prehearing investigation into the nominee’s background.

Second, it holds a public hearing, in which the nominee is questioned and may give testimony about everything from her judicial philosophy to her stand on abortion.

Finally, the committee will “report” its recommendation to the full Senate. The committee can report the nomination with a favorable recommendation, a negative recommendation or no recommendation.

If a majority of the committee opposes confirmation of the nominee, it can technically refuse to report the nomination, therefore preventing the full Senate from considering the nominee at all.

This hasn’t happened since 1881, and would deviate from the committee’s “traditional practice.” But that does not mean it is out of the question. The chairman of the committee, Republican Senator Chuck Grassley, has already said that, in his view, the Senate should not act on a Supreme Court nomination before the presidential election in November.

Step 3: The full Senate

Let’s assume that the committee does report the nomination to the full Senate.

There are 100 senators in the United States Senate – two for each state. Currently, the Senate is majority Republican, with 54 senators to the Democrats’ 44, with two independents for added flavor.

This is where it gets interesting, because the Senate follows rules so arcane and incomprehensible that otherwise reasonable writers freely refer to them as “insane.”

In order to consider the nomination, the Senate has to enter a special “executive session.” This is typically achieved by having the Senate majority leader ask for unanimous consent to have the Senate consider the nomination.

Unfortunately for the president, Republican Senator Mitch McConnell (R-KY), the current majority leader, has issued a statement saying that Justice Scalia’s vacancy should not be filled until after the November election. So McConnell appears unlikely to ask for unanimous consent to consider an Obama nominee.

If unanimous consent cannot be obtained (if it even is sought), the nomination can be considered if someone makes a motion that the Senate do so.

If the motion that the nomination be considered is made during a special “executive” session of the Senate, then the motion itself is debatable and can be blocked by filibuster – that movie-ready delay tactic in which which a senator recites Shakespeare, Dr. Seuss or recipes for fried oysters until everyone gives up and goes home.

Closing debate on the motion so that the Senate could move on to a vote would require a supermajority of 60 votes – again, unlikely given the current polarization of the Senate.

If the motion is made while the Senate is in its regular “legislative” session, then the nomination will be considered by the full Senate. But because of aforementioned arcane Senate rules, the vote on the nomination could also be blocked by filibuster.

Step 4: The vote

But let’s assume that the nomination does emerge from the Judiciary Committee, makes it to an “up or down” vote and weathers any filibuster attempts.

A vote to confirm then requires a simple majority of the senators present and voting. If all goes well, the secretary of the Senate will transmit the confirmation vote to the president.

The president then can breathe a sigh of relief and sign a commission appointing the person to the Supreme Court.

But I wouldn’t count on it.

The loophole

If the traditional 4-step process fails, there is one additional possibility open to the president.

Article II of the Constitution also says that the president “shall have power to fill up all vacancies that may happen during the recess of the Senate” and that the appointment can last until the end of the Senate’s next session – in this case, until late 2017.

A recess appointment would mean that the president could simply fill Justice Scalia’s seat temporarily without any input from the Senate.

As it happens, the Senate is currently in recess until February 22. What happens next is anyone’s guess.

Caren Morrison, Associate Professor of Law, Georgia State University

This article was originally published on The Conversation.