Donald Trump’s former campaign manager Paul Manafort turned himself in on Monday morning to face charges as part of special counsel Robert Mueller’s investigation into the Trump campaign’s ties to Russia. Rick Gates, Manafort’s previous business partner who also worked for the Trump campaign, is also facing charges.

I recently reached out to Renato Mariotti, who served as a federal prosecutor from 2007 to 2016 and who is now a candidate for Illinois Attorney General, and asked him what we can infer from Mueller’s aggressive approach to this case. He told me that Mueller is employing what he calls a “divide and conquer” strategy, meaning he’s looking to exploit conflicts between people under investigation in order to turn them against one another.

That Mueller’s team is homing in on Manafort, he adds, suggest two things: that they have the strongest case against him and that they believe he has incriminating information about other people under investigation.

Our full conversation, lightly edited for clarity appears below.

Sean Illing

Mueller’s approach to this investigation so far appears to be ultra-aggressive. Does that surprise you?

Renato Mariotti

First of all, I’d say that Mueller is being aggressive in his pursuit of Paul Manafort, but he’s not necessarily being aggressive in other aspects of the investigation — for example, toward the White House. The way he’s interacting with the White House is more typical of how I’d expect a prosecutor to interact with a defense team that is being cooperative and for which he has no reason to believe that there’s any threat of destruction of documents or evidence.

Sean Illing

Why is he being so aggressive toward Manafort?

Renato Mariotti

There must be some concern about the destruction of evidence; the mere fact that Mueller executed a search warrant as opposed to just issuing a subpoena suggests that. But what really confirms is the fact that Mueller got what’s called a “no knock” warrant, which requires him to demonstrate to the judge that there’s good reason why the FBI should not have to knock and announce their presence, and the only conceivable reason to do that is a concern about the destruction of evidence.

Sean Illing

There also appears to be a concerted effort to flip Manafort. Is that how you read it?

Renato Mariotti

Yes, that’s likely the other reason why Mueller is being so aggressive with Manafort. They want to flip him. People talk loosely in the press about Mueller wanting to flip Manafort against Trump, but there might also be others that he's looking to use him against, people that Manafort might have information on. What makes it most clear to me that Mueller's team wants to flip Manafort is the statements to him that in July notifying him that he will be indicted. That's the sort of thing that I've done as a prosecutor when I'm trying to flip someone.

Sean Illing

Relative to normal white-collar investigations, this one seems to be moving pretty quickly. Does that indicate anything to you?

Renato Mariotti

Mueller is proceeding on a fast pace for an investigation of this type and it seems to me that one primary driver of that is that, unlike most prosecutors, he's competing with parallel investigations, in this case congressional investigations, that don't necessarily have the same interests as he does. Congressional investigations are tasked with investigation something and making the public informed of the facts and are less concerned about ensuring that witnesses don't become aware of what other witnesses are saying.

So I think Mueller is rightfully trying to outrace the congressional investigation in order to gather as much evidence as possible and speak to as many people as he can before they become aware of what others might or might not have said to other investigators.

Sean Illing

Is the fact that they're homing in on Manafort more an indication of the evidence they have against him or of the information they suspect he has about the Trump campaign?

Renato Mariotti

It suggests to me that they have the strongest case against Manafort. So typically what you do when you're thinking about who to flip is you start with the people you have the strongest case against and then you decide which one of these people can provide you with the most incriminating information.

Sean Illing

Is Mueller’s divide-and-conquer strategy in this case a standard prosecutorial approach to these sorts of investigations?

Renato Mariotti

It's always the case that prosecutors seek to magnify and exploit the conflicts between the different people that they're looking at. That's a pretty common prosecutorial strategy. And it appears to be working based on the latest reports we've seen. We can see deep divisions within the Trump team, and they're apparently concerned about people wearing wiretaps.

That's exactly the sort of climate Mueller wants to create.

Sean Illing

How do you see this case unfolding?

Renato Mariotti

I've always said that I didn't expect any decisions about charges to be made until 2018, and that's because typically prosecutors wait until the end of their investigations to make those decisions and the only reason they would not is if they reached a wall in terms of their progress and they felt that indicting someone might move forward the prospect of flipping that person.

From what I can tell, Mueller and his team are waiting on documents from the White House. They still have many interviews scheduled. So I wouldn't expect to see any conclusion of this until next year.