(CNN) — As President Donald Trump and Attorney General Jeff Sessions continue their war of words, the question has once again arisen of what would happen at the Justice Department is Sessions leaves.

There’s no immediate indication Trump is ready to fire Sessions, or that Sessions is ready to quit, but here’s what could happen if the attorney general’s office is empty:

1. Who is immediately in charge?

If Sessions is fired, then Deputy Attorney General Rod Rosenstein, the current No. 2 at the Justice Department, would automatically take his place — at least, according to statute and the President’s own executive order detailing the succession plan from March.

But just as Trump has been unhappy with Sessions for recusing himself from the investigation of Russian interference in the 2016 election, he hasn’t had kind words for Rosenstein, the man now overseeing the work of special counsel Robert Mueller.

If Sessions and Rosenstein are both fired (or quit), then in that case, Solicitor General Noel Francisco, would elevate to acting attorney general.

And moving even further down the line of succession — if Sessions, Rosenstein, and Francisco are all gone, then Steven Engel, Assistant Attorney General for the Office of Legal Counsel, would be the next person taped to serve as acting attorney general. The line of succession after Engel, as of now (based upon which officials have been Senate confirmed), is Assistant Attorney General for the National Security Division John Demers, followed by Assistant Attorney General for the Criminal Division Brian Benczkowski, followed by the current US Attorneys for the Eastern District of North Carolina and the Northern District of Texas.

2. Can Trump pick someone else entirely?

Yes — the President doesn’t have to follow the usual course, but this is where things could get tricky.

Under the Federal Vacancies Act, Trump can pick anyone who holds a Senate-confirmed position to serve as acting attorney general (subject to certain time limitations) — but the person he selects as acting cannot then be named as the permanent successor.

By its terms, the law applies whenever a Senate-confirmed officer in an executive agency dies, resigns or is “is otherwise unable to perform the functions and duties of the office.”

But it’s an open question as to what happens if the officeholder is instead fired by the President.

As a result, legal experts have questioned whether an acting attorney general would be a valid appointment if Sessions is fired. But there’s always the question of who has standing to challenge such an appointment, and Rosenstein may not be inclined to take that to court.

3. What about a recess appointment?

Another option is for Trump to announce a replacement for Sessions during the next Senate recess — a so-called “recess appointment” who could then serve until the end of the next congress.

Trump hasn’t hinted at this possibility, but Senate Democrats would almost certainly try to block it.

While Republicans control the Senate now, the only way they can formally adjourn (which would set up a period when recess appointments are available) is to pass an adjournment resolution. However, Democrats can filibuster that resolution, which they would do to prevent Trump from making a recess appointment.

As a result, in a practice that carried over during President Barack Obama’s term, the Senate has scheduled several pro forma sessions — basically it comes into session for a couple minutes every few days — in order to prevent a long recess that would allow a president to make a recess appointment.

4. What happens to Mueller’s investigation if Sessions is out?

Speaking of Mueller — the recusal is the primary reason Trump has unleashed a fury on his attorney general.

For the time being, only Rosenstein currently has the power to remove Mueller for “misconduct, dereliction of duty, incapacity, conflict of interest, or for other good cause, including violation of (Justice) Departmental policies” under the special counsel regulations.

But if Sessions is fired, and his replacement doesn’t have the same a conflict overseeing the investigation, then Rosenstein would no longer be in charge, and Trump’s new attorney general could potentially fire Mueller.

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