Renato Mariotti is a former federal prosecutor and a partner at Thompson Coburn LLP. He is a Democratic candidate for Illinois Attorney General.

Rumors are flying that President Trump will soon fire special counsel Robert S. Mueller III. Over the weekend, Trump transition lawyers alleged wrongdoing on Mueller’s part. Last week, Republican members of Congress grilled Deputy Attorney General Rod J. Rosenstein, challenging Mueller’s legitimacy and objectivity. Conservative commentators have called for Mueller to be investigated, while others have called for him to resign.

Concern that this would undermine the rule of law has gotten so serious that the liberal activist group MoveOn.org has organized a rapid-response plan for protests if Mueller is fired, with the specific timing determined by when in the day the news breaks. On Sunday, though, Trump insisted that he will not fire Mueller but is contemplating firing Rosenstein or Attorney General Jeff Sessions, realizing that firing Mueller would be a “step too far,” according to The Washington Post.

Why would Trump hold off on firing Mueller? Because if his goal is to undermine the investigations into Russian interference in last year’s campaign, keeping Mueller around is probably the best way to do it.

Firing Mueller would not end the investigations that the former FBI director leads. Although we often speak about the “Mueller investigation,” inside the Justice Department that term probably refers to several different but related investigations. Some of those, such as the investigations of Paul Manafort and Michael Flynn, began before Mueller was appointed. Others, such as the inquiry into obstruction of justice, began later.

Those investigations would go on even if Mueller leaves. When the Justice Department initiates an investigation, it can’t be closed without following a set of procedures that ensure cases aren’t shut down for improper reasons. If a case is opened, it can’t be “declined” — closed without bringing charges — without a detailed justification for closing the case. As a former federal prosecutor, I’ve declined my share of cases, and it takes time. Declining even a routine case requires a written explanation justifying the declination, citing specific reasons that are consistent with Justice Department guidelines. In more complex or high-profile matters, much more extensive memorandums are prepared. Once in my career, I inherited a complex case that another prosecutor unsuccessfully sought to decline, and I ultimately charged the case.

Any cases Mueller’s team is working on wouldn’t magically decline themselves if Mueller is fired. The reports of interviews in the FBI computer system wouldn’t delete themselves. The documents and other evidence collected by Mueller’s team of FBI agents and prosecutors wouldn’t destroy themselves, either. In fact, Justice Department procedure is to retain evidence for years even after a file is closed. Whenever I closed a file, I had to specify how many years the evidence would be retained.

Trump’s legal team is probably aware of all of this and has probably considered exactly what would happen if Mueller was removed. While I doubt they’ve communicated all of the specifics to him personally, their strategy is surely informed by a knowledge of how the Justice Department works and a desire to contain any damage caused by Mueller’s investigation.

Firing Mueller would put Rosenstein in charge of the investigations instead of Mueller. Rosenstein recently defended Mueller before Congress and strongly suggested that he approved of the direction of the investigations. If Trump fired Mueller, Rosenstein could appoint a replacement. Or if Trump ordered the repeal of the special counsel regulations governing the investigations, Rosenstein could appoint a Justice Department prosecutor to oversee the investigation.

What if Trump fired Rosenstein and Mueller? Or fired Sessions and Mueller? Firing Mueller would generate massive protests and could spur Congress to take up new legislation to establish an independent counsel. If Mueller was fired improperly, he or others could initiate legal action to fight the termination, keeping the story in the headlines. Firing him would give Trump the opportunity to replace Mueller with someone who was determined to undermine the investigation. But it would have significant downsides.

For example, if the new special counsel swiftly ended the investigations, Congress and the public might conclude that Trump and/or his associates were guilty of serious crimes and that replacing Mueller was part of a coverup. If the new special counsel improperly terminated an investigation, prosecutors and FBI agents might come forward and accuse him or her of wrongdoing. That could ultimately generate new criminal liability for anyone involved.

If a new special counsel permitted the investigations to go forward, though, that could be the worst of all worlds for Trump. Democrats would assume that the new special counsel was biased on Trump’s behalf, and Republicans would be less likely to distrust a new special counsel than they are to distrust Mueller, who has been the subject of intense attacks in conservative media. So if a new special counsel found that there was insufficient evidence to charge Trump, the decision would be called into question, even though a similar determination by Mueller would be hard for Democrats to second-guess. On the flip side, if a new special counsel took aim at Trump and his inner circle, it would be harder for Trump to call it a “witch hunt.”

All that means is that ultimately, keeping Mueller around but continuing to attack him and the FBI is probably Trump’s best strategy. As a patriot and former federal prosecutor who thinks that we should respect the men and women of the FBI and Justice Department, I find this strategy appalling. But I recognize that it is Trump’s best remaining move. It remains to be seen whether he has enough discipline to stay the course.

Read more: 

If Trump plans to fire Mueller, he should do it sooner rather than later

Sitting presidents can’t be prosecuted. Probably.