Andrew C. McCarthy, a former chief assistant U.S. attorney, is a contributing editor at National Review and a senior fellow at National Review Institute who has written extensively on the Russia probe.

The Daily Signal’s Ginny Montalbano spoke exclusively with McCarthy about the year-old special counsel’s probe and the president’s vulnerability after McCarthy’s May 15 appearance on a panel at the 2018 Bradley Symposium, “The State of the Constitution,” hosted by The Heritage Foundation. What follows is a lightly edited transcript of the interview.

Ginny Montalbano: Thank you for being with us today. I’d like to start by asking you, what does the Trump-Russia investigation say about the state of our Constitution?

Andrew McCarthy: Well, it says that we’re quite far removed from the original assumptions of the framing, which would have been that … the way that you check excessive or illegal or abusive presidential or executive activity would be by constitutional means, political means, checks by the legislature on the executive. Mainly the power of the purse. Ultimately, the impeachment power.

There was never really an intention or even an inkling, I would say, of a federal prosecutor in a constitutional system as designed, conducting the kind of investigation we’re seeing to rein a president in.

In fact, we didn’t have a Justice Department really until around 1870. The FBI, which is investigating the case involving the president and Russian interference in the election, didn’t even exist until 1908. Clearly, what the framers had in mind was that it would be Congress that would check the president, not a federal prosecutor. We’ve come a great distance from our founding.

Montalbano: What evidence is special counsel Robert Mueller assembling against President Trump?

McCarthy: It’s very difficult to tell because most of this investigation has taken place in secret. Most of the documentary support for it is secretive. This actually makes it quite different from other independent counsel-type investigations we’ve had in modern history, whether it was Watergate or Iran-Contra or the Whitewater investigation that became the Lewinsky investigation. In each of those cases, the president, the public, the media, everybody knew what was under investigation and what the allegations were.

Because this investigation has really occurred under the cone of what’s known as a counterintelligence investigation rather than a criminal investigation, the result has been that we really don’t know everything that Mueller is looking at.

Counterintelligence is classified. Basically, it is how we define the actions and intentions of foreign powers. The objective of it is not to build a criminal case. Ordinarily, even if there were a criminal element to counterintelligence investigations, it’s not something that we would know. That’s made it very difficult to understand what it is that Mueller is driving at.

Montalbano: On that note, as you just mentioned, a counterintelligence investigation is not a criminal investigation. Do Americans recognize the difference?

McCarthy: I don’t think so. One of the unfortunate things here is that they’re both called investigations and they’re both conducted by the FBI. I think people who are foreign to this and it’s not part of their experience can be forgiven for not recognizing the difference. The difference actually is quite critical.

Counterintelligence operations are conducted basically for the president in order to assist the president in his national security mission. The president’s most important responsibility, which is defense of the country from foreign threats. Counterintelligence is supportive of that mission. It mainly involves not criminal activity, but information gathering.

Very often, it has to be classified because what you’re dealing with are innocent people who may be suspected of bad activity, but may actually just be cooperating with the law enforcement, or I should say the intelligence officials, of their country.

In order to protect their identities and to encourage them to cooperate, things need to be kept secret. It’s a very different beast than criminal investigations, which are in some sense conducted in secret. For example, grand jury proceedings are secret. When a prosecutor goes to a court to try to get an arrest warrant or a search warrant, that’s done in the judge’s chambers with no defense lawyers obviously present.

A lot of the criminal investigative process is done confidentially. But the important difference is it’s done with an eye toward the understanding that eventually, there will be a public prosecution where everything will be unsealed. Everything will be disclosed that needs to be disclosed to the defense lawyers, and it will be tested in a public proceeding.

It’s a very different way of assuming how a probe is going to go than a counterintelligence investigation, which, frankly, is classified and which we never expect to find anything out about.

Montalbano: Do you feel that the Mueller investigation was always about impeachment?

McCarthy: Well, the short answer is yes. Let me explain why. I should preface this by saying I don’t mean to suggest that Mueller necessarily is trying to impeach the president or that he believes the president should be impeached. What I mean is that because of the structural protections that a president has from being indicted, no experienced federal prosecutor would go into an investigation like this.

Robert Mueller is a highly, highly experienced, sophisticated former federal prosecutor and FBI director. Nobody of his experience certainly would go into this thinking that you could indict the president.

In fact, there’s Office of Legal Counsel opinions at the Justice Department, which are binding on Mueller, which say that a sitting president can’t be indicted. What I’ve always thought is that this investigation has really been about, is there a basis to impeach the president? Again, it doesn’t mean the prosecutor wants to impeach the president, but I do think he thinks his mandate is to investigate that.

Montalbano: Now why do these special prosecutor probes often end in a far different place from where they originally began?

McCarthy: I think the special counsel, or as it’s been known, special prosecutor, independent counsel … it’s had different iterations over the years. I think it’s a pernicious institution because what it essentially is, is the assignment of a single prosecutor and his staff to a single target or set of targets.

While that may not seem strange to the uninitiated, in a normal federal prosecutor’s office every case has to compete with every other case for resources and attention, which means the ones that are worth pursuing get pursued and the ones that aren’t, don’t. They basically fall by the wayside. Those cases get closed and people move on.

What you have in a special counsel situation is one prosecutor with essentially unlimited resources, who is trained on a single target. Because of that dynamic, what tends to happen is that if the prosecutor doesn’t find whatever crime was suspected when the investigation commenced, whatever crime was the rationale for opening the investigation in the first place, by now you’ve pored through the background of the target that you’re looking at, and the target’s associates, and you’re finding other things.

What you end up doing inevitably is expanding the investigation. Often, you expand it until you finally find something that you think is worth prosecuting.

Of course, the public relations dynamic here—and it’s a big problem—is that it seems that a lot of people think that the measure of success for a special counsel is whether you bring charges, whereas in point of fact, the measure of success for any prosecutor is whether justice is done. What that means in a case where there’s insufficient evidence is precisely that you don’t bring charges.

Montalbano: At the symposium you spoke about the structure of executive power. On that note, should President Trump fire anyone?

McCarthy: Well, I think we have to see how it plays out. One of the important aspects of this really being an impeachment structure or an impeachment case rather than a criminal case is that we’re really in more of a political environment than a legal one.

Impeachment is a political process. It’s not a legal one. What I mean by that is a legal process takes place in a judicial court, and the law is that if the prosecutor proves all of the elements of the offense beyond a reasonable doubt, the jury is bound to convict. Now the jury can always nullify, but that’s frowned upon. Basically, if you prove the case in a court proceeding, you’re supposed to get the result. The conviction, in this case.

Impeachment is very different. Impeachment, being political, means that it’s the political process that was designed by the framers in the Constitution, borrowing from British law for the legislature to rein in rogue executive officials. Also other officials, but primarily the executive branch. In particular, the president.

The standard that’s used, which again is borrowed from British law, is “high crimes and misdemeanors,” which are not necessarily indictable offenses. They can be, but they’re more in the nature of abuse of power than violation of penal laws.

It’s basically abuse of the public trust that is reposed in the president or other executive officials. The real political aspect of it, and I think the genius of the framers in this regard and the reason why impeachment has been so rarely used, and never really used successfully in our country’s history, although I think Nixon probably would have been impeached: You … can file articles of impeachment against a president by a simple majority vote in the House. To remove a president from office requires a supermajority vote of two-thirds of the Senate.

What that necessarily means is that no president will be removed from power unless something so egregious has been done that it cuts across partisan and ideological lines and represents a consensus within the country broadly that the president has done something so abusive that the president needs to be removed from power.

I think, interestingly, the dynamic of the Clinton presidency is very interesting in this regard because Clinton’s approval numbers actually went up during his administration while he was being investigated for potential impeachment and while the impeachment proceedings went forward.

I’ve always thought that that didn’t mean that the American people approved of his behavior. I think far from it. Those approval polls at the time were a proxy for “Do we want this guy removed from office or not?”

It’s a political process and it’s an ingenious one, because it means that impeachment will be reserved for the extreme cases that are really warranted.

Montalbano: Thank you so much for being with us.

McCarthy: Thanks so much.