The FBI raided Michael Cohen’s office and hotel room on Monday, and what we know about who did the raid is just as important as the information we have on why they did it.

The raid was by the U.S. Attorney’s Office for the Southern District of New York, and not directly by Robert Mueller’s special counsel’s office. Mueller’s team referred the case to the U.S. attorney, but the U.S. attorney sought the search warrant and received it only after establishing probable cause. In searches of such high-profile and sensitive subjects, U.S. attorneys usually need approval higher up in the Department of Justice.

Why might this U.S. attorney’s office have been involved? One answer is the most basic: a raid of at least two locations simultaneously—office and hotel—requires a lot of bodies and coordination. If you need that many FBI agents, you already need to coordinate with the local office for it to go smoothly. Former prosecutors say that Mueller might have referred this raid to the Southern District for logistical reasons alone. But he still chose to refer the investigation to this U.S. attorney’s office rather than simply use their logistical support.

What else might this move tell us about Robert Mueller’s thinking? First, remember that Mueller has learned that Trump has already tried to fire him, and the person who reportedly stopped him—White House counsel Don McGahn—is rumored to be on his way out of the administration.

The Post is reporting that the subject of the Cohen warrant was an investigation into possible bank fraud, wire fraud, and campaign finance violations, possibly related to a hush money contract with adult film performer Stormy Daniels. Mueller probably could have made a claim that Cohen already fell under his jurisdiction, which is to investigate Russian election interference, links between the Trump campaign and Russia, and “any matters that arose or may arise directly from the investigation.” But it has been reported that Deputy Attorney General Rod Rosenstein made the call to involve the U.S. attorney, and perhaps Rosenstein made a strategic calculation about Trump, or they agreed together. It seems, though, that both men know they need to spread Mueller’s work around as a hedge against his firing, and maybe even to try to deter Trump from firing him.

In comments after the raid, Trump attacked Mueller, Rosenstein, and Attorney General Jeff Sessions, hinting ominously about what he might do next. Mueller and Rosenstein may have anticipated that this raid might have been the last straw for Trump, triggering their firings as they get closer and closer to Trump’s inner circle and any potential personal criminal liability. Once other prosecutors’ offices are involved and have gathered evidence of crimes, though, Trump receives less benefit from firing Mueller, and at an increasing cost. And even if Trump fires Mueller, more prosecutors can carry on the work, with access to some of the same material. Trump should not be able to fire Mueller under the DOJ’s rules or under the Constitution, but Mueller and Rosenstein understand they need to have an emergency backup for a president who does not care about those rules.

Second, Mueller’s move also suggests that he trusts some prosecutors to cooperate, that he trusts Rosenstein to keep up his supervision, and that he at least has sufficient hope that Sessions will stay out of the way. Sessions’ firing of FBI Deputy Director Andrew McCabe did not inspire confidence that he would recuse himself fully from the Russia investigation, but Mueller must have some assurances from Rosenstein that the investigation can proceed in the DOJ.

Third, Mueller may be thinking about politics and legitimacy. The right-wing pundits and Fox News commentators have been complaining that Mueller has exceeded the scope of the Russia investigation. (They did not seem to mind when special counsel Kenneth Starr moved from a land deal to a blue dress.) Anyone who has followed Cohen’s career knows there are obvious connections to the Russia investigation. Even if these conservative attacks are not legally sound or morally consistent, they nevertheless might give Trump cover to fire Mueller, and they might give Republicans cover to tolerate his firing with just enough handwringing and finger-wagging but no real action.

So, Mueller may be engaging in a political strategy: Monday’s raid does not fit the right-wing narrative of a deep-state Inspector Javert out of control, but instead, it involves more traditional law enforcement officials and even more Trump appointees. The Southern District is the most establishment prosecutors’ office in the country, which might still open up attacks on “the deep state” from the fringe right and the Trump dead-enders, but mainstream Republicans know better. U.S. Attorney Geoffrey Berman is viewed as a reliable nonpartisan professional who served in Republican administrations. Sessions appointed Berman as U.S. Attorney for the Southern District after Trump interviewed him. It would be ridiculous to attack Berman as a Democratic mole. [Update, April 10: ABC News has reported that Berman is recused from the investigation.]

If Mueller himself led the raid, the right-wing media could have more plausibly accused him of crossing a red-line if he seemed to be pursuing such Stormy seas. Mueller did not push this Starr-crossed envelope, though. He kept his ship in calmer waters and shored up his legal and political legitimacy with other legal institutions signing on.

Fourth, this raid involved not only the U.S. attorney’s office, but also a federal judge or magistrate judge signing off on the search warrant on the president’s lawyer after finding probable cause of criminal acts. That’s a big deal. A magistrate is not a federal judge, but they are appointed by federal judges, and they are not going to mess around in such a high-profile case. The prosecutors had to show not only probable cause of a crime, but they probably also had to persuade the magistrate that attorney-client privilege did not protect against the raid. Prosecutors likely had to convince the magistrate that at least some of the evidence would fit the crime-fraud exception to the privilege, and that bar is usually set very high. In such cases, it is important to have a separate team of investigators examine the evidence to separate protected communication from unprotected, which is another reason to involve the U.S. attorney, because the office is probably better able to provide two separate teams to honor the attorney-client privilege.

Fifth, Mueller may simply realize that his team already has too much work to prosecute Cohen for campaign finance felonies. That case seems relatively straightforward: Cohen allegedly made an illegal campaign donation willfully. When John Edwards’s campaign did something similar, the DOJ prosecuted. Let the DOJ handle this aspect of the Stormy case quickly, and meanwhile, Mueller is free to speak with Cohen’s attorneys and see if he might want to make a deal on the more direct Russia investigation—though given his loyalty to Trump, this seems like a long shot. But maybe Cohen’s documents will be enough, without Cohen’s active cooperation.

Finally, anyone who has been following this investigation knows that Michael Cohen’s involvement is more than just hush-money for his client’s sexual adventures. Various journalists, such as Josh Marshall, have shown that Cohen is deeply implicated in Trump’s business in Russia and potential financial crimes over many years. If Putin has kompromat on Trump, it may actually be evidence of such financial crimes. If Cohen knows where the bodies are buried, Mueller may be one step closer to knowing, too. And significantly, more prosecutors’ offices may be closer to knowing, as well.