As this is being written, it’s not clear whether Deputy Attorney General Rod Rosenstein’s offer to resign his position at the Justice Department will be accepted. If President Trump accepts his resignation, there would be significant repercussions for special counsel Robert S. Mueller III’s investigation into Russian election interference.

But perhaps not the ones you might expect.

You’ll remember that it was Rosenstein who appointed Mueller to his position in May 2017. That task fell to Rosenstein because, two months prior, Attorney General Jeff Sessions recused himself from decision-making related to Russia (a decision that infuriated Trump). There’s an argument that Sessions could simply unrecuse himself and assume control of the investigation, but that would kick off a legal fight that would probably end up in the Supreme Court.

On Russia matters, Rosenstein is the acting attorney general, given Sessions’s recusal. If Rosenstein leaves his position, the Mueller probe would probably fall under the authority of Solicitor General Noel Francisco, as this chart indicates.

There would be someone who stepped in to serve as acting deputy attorney general. That, though, introduces another problem, outlined by the Brennan Center’s Victoria Bassetti earlier this year. It’s not clear that someone can be both an acting deputy attorney general and an acting attorney general (given Sessions’s recusal). That’s the same problem that affects acting associate attorney general Jesse Panuccio, who stepped in after Rachel Brand resigned her position this year.

So Francisco, having been confirmed by the Senate to his position, is the assumed next-in-line for the Mueller probe. Unless, that is, he has to recuse himself given his former law firm’s involvement in the Trump campaign. (A possibility raised on Twitter by former Office of Government Ethics head Walter Shaub.) In that case, the job would probably go to Steven Engel, the assistant attorney general for the Office of Legal Counsel.

At least until a permanent replacement for Rosenstein is appointed, which is where things get interesting.

In 1998, Congress passed the Federal Vacancies Reform Act, which refined the process allowing a president to fill a vacancy in the government. One of the lesser-known provisions of that bill is that the president — in this case Trump — can fill a vacancy in a Senate-confirmed position with anyone who has already been confirmed to a position by the Senate. In other words, Trump can allow Francisco to run the probe — he could move over anyone else in his administration who already ran the Senate gantlet. That means any of the 350-plus people on The Post’s confirmations tracker. (The position includes the word “attorney,” but there’s no requirement that the person who holds that position have a law degree.)

In July 2017, we spoke with Georgetown University law professor Paul Butler, who said the Vacancies Act was Trump’s best bet for getting someone friendly in charge of the Mueller probe specifically because he could slide over anyone he wanted — and wouldn’t have to risk a Senate confirmation process.

But Butler noted a catch: It wasn’t clear whether the law applied if the person was fired from his position. It stipulates only that the president has that authority if the person in the position “dies, resigns or is otherwise unable to perform the functions and duties of the office.” If Rosenstein resigns, it’s clear-cut. If he’s fired? Things get tricky and, again, probably end up at the Supreme Court.

Let's say Trump fills the spot with someone friendly, meaning someone who's willing to try to undercut the Mueller probe. How much damage could that person do?

A lot.

In April, we spoke with Louis Seidman, Carmack Waterhouse professor of constitutional law at Georgetown University. He explained that, despite the independence built into the special counsel position, there were key points of leverage that a hostile overseer could exercise.

First and foremost, whoever is the Department of Justice staffer overseeing the probe is granted the power to “request that the Special Counsel provide an explanation for any investigative or prosecutorial step, and may after review conclude that the action is so inappropriate or unwarranted under established Departmental practices that it should not be pursued.” In other words, if Mueller wants to bring forward a new indictment, the person in charge at DOJ could nix it.

They could also go further.

“Depending on how aggressive this person wanted to be, they could dismiss the criminal cases, they could get rid of the grand jury,” Seidman said at the time. “In the end, if Trump is determined, the people he appoints could shut [the probe] down.”

So if Rosenstein’s resignation is accepted, Trump could fill his position with someone who has already been Senate-confirmed, and that person could essentially block new indictments and unwind what Mueller has already done. There would be political backlash, certainly, but it could be done.

That wouldn’t offer Trump complete protection, of course. There is an existing investigation into the Trump Organization in New York, which would continue regardless of what happens to Mueller’s team. But a Rosenstein resignation could significantly lower the heat Trump feels from Mueller, should his replacement want it.

And if Rosenstein actually resigns.