ROBERT COSTA: A high-stakes standoff.

President Trump and his allies clash with the Justice Department.

I'm Robert Costa.

The Russia probe enters its second year, tonight on Washington Week.

PRESIDENT DONALD TRUMP: (From video.)

I have this witch hunt constantly going on for over 12 months now and actually much more than that.

ROBERT COSTA: As President Trump continues to insist there was no wrongdoing by his 2016 campaign, the Russia probe hits the one-year mark and the president gets behind allies in Congress who are pushing to discredit Robert Mueller's ongoing investigation.

The latest development: a showdown over a top-secret FBI source.

FBI Director Christopher Wray issues a warning and the bureau scrambles.

FBI DIRECTOR CHRISTOPHER WRAY: (From video.)

The day that we can't protect human sources is the day the American people start becoming less safe.

ROBERT COSTA: Plus, a new plea deal involving the former son-in-law of Paul Manafort that could put new legal pressure on Trump's former campaign chairman.

Despite the ramped-up efforts against Mueller, Mr. Trump's personal attorney, Rudy Giuliani, says he's more hopeful about the possibility of a sit-down interview between the president and the special counsel.

Others remain skeptical or urge against it.

RUDY GIULIANI (attorney for President Trump): (From video.)

We had the first hopeful communication with him last night.

I don't want to dismiss it because I think it was a good-faith attempt to really narrow the focus quite dramatically of the questioning.

ROBERT COSTA: We discuss where the investigation and the president go from here with Yamiche Alcindor of the PBS NewsHour, Devlin Barrett of The Washington Post, Kelsey Snell of NPR, and Mark Landler of The New York Times.

ANNOUNCER: This is Washington Week.

Once again, from Washington, moderator Robert Costa.

ROBERT COSTA: Good evening.

It has been a year - a year since Robert Mueller and his team began their special counsel investigation into Russian interference during the 2016 presidential election.

The expansive federal probe has gripped the White House and Congress, and certainly newsrooms.

So far, Mr. Mueller has charged 19 people, including four former Trump campaign advisors and three Russian companies.

He has secured five guilty pleas along with their cooperation.

This week President Trump marked the one-year anniversary of the probe with criticism and suspicion - suspicion of the government he leads and longstanding institutions: the Department of Justice and the FBI.

On Twitter he slammed the special counsel as, quote, the "greatest Witch Hunt in American history."

He also tweeted "the Obama FBI 'SPIED ON THE TRUMP CAMPAIGN WITH AN EMBEDDED INFORMANT.'

Andrew McCarthy" - a conservative former federal prosecutor - says, "If so, this is bigger than Watergate!"

But let's take a step back, get up to speed on what this all means.

In brief, the president is echoing a claim being made by his allies on Capitol Hill.

They believe the Russia probe, including the surveillance process of Trump campaign associates, was mishandled by the DOJ and the FBI.

That belief has led them to push Justice for more documents, and the latest firestorm is over a top-secret source - a source who provided information to the FBI.

Republicans and the president want more information.

DOJ officials, however, are worried about the source's safety, which they believe could be in jeopardy if exposed.

Last week, The Washington Post, including Devlin Barrett, who joins us tonight, reported that the source is at the center of this back and forth between House Intelligence Committee Chairman Devin Nunes and the DOJ.

So what was a congressional outcry now has presidential support.

Devlin, welcome to Washington Week.

Talking to a source last night I heard that this is a firestorm inside of the White House.

One person described it as a tinderbox, this fight between the DOJ and the GOP and now the president of the United States.

At Justice tonight, are they on edge?

DEVLIN BARRETT: I think they are not on edge, but they are prepared for this to escalate - the possibility of escalation, because for a lot of folks in law enforcement this fight over this source - while an important fight on the merits - is really about a bigger problem and a bigger set of confrontations, which is really about is Rod Rosenstein going to stay as the deputy attorney general overseeing this investigation?

Is the Congress going to turn this fight over the documents into a fight over who gets fired or who quits inside the administration?

Is the Mueller probe going be to allowed to continue?

Or is there going to be some sort of ultimate confrontation between the White House, Republicans in Congress, and the Justice Department?

ROBERT COSTA: What does that mean, Devlin, when you say the escalation - that ultimate confrontation?

Does it mean the president issues a direct order for these classified materials to be released to the public?

DEVLIN BARRETT: Certainly with the folks in Congress, the Republicans in Congress who are angriest at the Justice Department about this, they want the president to issue that order.

But the Justice Department, and to a lesser extent the intelligence community, have made pretty clear that that is a red line for them, that that is a very hard order to carry out, in their minds, because they do genuinely worry that it would endanger not just the source, who everyone is trying to protect, but people who have helped the source over the years.

And so they feel that they are on very firm legal and moral grounds to say no.

And then, just gaming it out, if that order were to come, and if that order to be essentially refused, what does the president do then?

And that's when - what goes to your earlier point about a tinderbox.

That is the - sort of the worst-case scenario of an ultimate confrontation that could happen as a result of all this between the White House and the Justice Department.

ROBERT COSTA: This charged moment, Kelsey, the president waded into it, pushed it forward this week.

But when you think about how it's been building over time, it started on Capitol Hill, Congressman Mark Meadows of North Carolina, a Republican, Chairman Nunes of the Intelligence Committee, people who were close to President Trump.

What have they been saying to him?

KELSEY SNELL: They have been saying that he's right, and that this is a witch hunt.

They have been saying that they can follow through for him in Congress in making more pressure build.

The problem is, though, they are actually just a small portion of the Republican Party on the Hill.

There are a lot of people that I talk to who say that there is a leadership firewall here that needs to be maintained if - you know, if we're not going to have the tinderbox situation, like you're talking about.

So far, House Speaker Paul Ryan and Majority Leader Mitch McConnell say that they are supportive of Mueller finishing his investigation.

They say they'd like it to wrap up quickly, but they are staying out of the hyper-partisanship of this.

And as long as there is this leadership firewall between the talk in the Freedom Caucus - which is the group that is run by Mark Meadows and was formerly run by Jim Jordan - as long as that is contained to just that small group, there is some hope among more mainstream Republicans that it will - it will stay that way.

ROBERT COSTA: But containment is a tough thing.

When you see, Mark, in the conservative media people like Steve Bannon, the former White House chief strategist, are out there pushing Meadows and Nunes along, what does that tell you?

You've covered Bannon for a long time.

When you see people like Bannon and people on Fox News pushing the administration, does that make it harder for the Republican leadership to control the situation?

MARK LANDLER: I think it does, because I think these people have a very astute read of what appeals to their base and what galvanizes their base.

And so this top-secret informant is a perfect test case.

You call the person a spy.

We don't actually know.

A lot of details haven't yet come out.

You put out this very sinister kind of portrayal of who this person is.

And it evokes all the worst kind of sense of the deep state and government agencies overstepping their bounds.

It's enormously powerful with Trump's base.

And I think it does resonate with some percentage of the Republican - of Republican voters generally, which is why when you look at polling data on questions of do you think the Mueller investigation is legitimate or is being conducted properly, broadly speaking you see support for it.

But if you look at the numbers within the Republican Party, a significant percentage of Republican voters believe that this is an investigation that's run amok.

So to some extent, I think they have already succeeded in discrediting this investigation so that when Mueller finally does file his report, X percentage of Americans will simply not believe it, on the face of it.

ROBERT COSTA: But there have been a lot of threats, Yamiche, from the president and his allies.

But the president has yet to pull the trigger when it comes to firing the deputy attorney general or making a move on the Mueller investigation.

Who's holding him back from that inside of the White House?

Is it Chief of Staff John Kelly?

Is it White House Counsel Don McGahn?

YAMICHE ALCINDOR: I'm not - in some ways, it's hard to tell who the president is listening to in terms of the person that's actually having the most weight in the moment, in the day.

I think the larger picture is that the Republican leadership - I think it would throw people into a sort of constitutional crisis if the president started firing Rod Rosenstein, if the president started trying to end the Mueller probe.

So I think that Republicans on a whole, the feeling that he's getting from his own party - whether it be from John Kelly or whether it be from Republican leadership like Mitch McConnell, it's the fact that, like, if you do this, this is going to be really, really bad.

And all the things that you want to do - the EPA, the DOJ, all the things you want to do on trade, even, I would say, your meeting with Kim Jong-un and all the things that you can be doing with North Korea - all of that would be thrown out of the window if you fired Robert - if you fired Rod Rosenstein and then tried to stop the Mueller probe, because everyone would then be laser-focused on that.

But I think the larger picture here, when I think about where we are a year from now, it's really critical what Mark said.

It's this idea that for a long time the president has been laying the groundwork to say Robert Mueller - who is a Republican, and I always like to remind people of that - that he is some hyper-partisan hack that is basically after him because people are mad that President Trump is president, and people want to somehow get rid of him.

And that idea has been something that they've been working on for a long time.

I think Rudy Giuliani coming out this week saying that the Mueller team has told President Trump's lawyers that they wouldn't indict a sitting president, and that they might issue a report, I think that that's laying the groundwork to say, look, this report, it's not even really that big of a deal, because they can't really do all the things that they want to do.

ROBERT COSTA: What about the origin of the probe?

We've seen some reporting from the Times this week about the Crossfire Hurricane, code name for the probe at the start.

You think about the source that we've been reporting on at the Post.

Are there legitimate questions about how this investigation was started?

Is the Department of Justice or FBI vulnerable here to congressional scrutiny, public scrutiny at some level?

DEVLIN BARRETT: I think most lawyers would tell you no.

I think most lawyers would tell you this is how investigations work.

But, you know, in many ways, what the Trump administration and his people have decided on is a sort of political solution to a legal problem.

It is both, obviously - it is both a legal problem and a political problem.

But they are really pouring, you know, as much energy as they can into the political strategy of trying to deal with this legal problem.

But in terms of the origins of the investigation, the way I think is easiest to understand it is the FBI was looking at a bunch of different things at a bunch of different times.

And that eventually coalesced into a bigger, larger, more scary question to them, which was: Is the Trump campaign itself, or senior people in the Trump campaign themselves, actively engaging with a foreign power to influence the outcome of our election?

That is the basic question.

And when you talk about it's been a year, we still actually don't have the answer to that basic, fundamental question.

And I do suspect that, in time, the public may get impatient for an answer to that basic question.

But right now, this is still a lot of legal blocking and tackling among the individual players.

And in that, so far, Mueller's been pretty successful.

ROBERT COSTA: And it all comes down to Carter Page and George Papadopoulos, these Trump campaign advisors back in 2016 - who they were meeting with, what they were doing.

MARK LANDLER: And were, in fact, they having conversations with people more senior in the Trump organization?

Were they bringing things to the Trump organization, to the Trump campaign, that the campaign was receptive to?

I think, just to pick up on one thing Dillon said - ROBERT COSTA: Devlin.

MARK LANDLER: Devlin.

I'm sorry, Devlin.

My apologies.

The question of was the origins of this investigation, were they proper or not, has to be seen within the broader context of a very charged political environment.

And you can't really talk about the beginning of the Trump investigation without talking about the end of the Clinton email investigation, because just as the FBI properly said nothing about the Trump investigation, James Comey did speak publicly about the Clinton email investigation.

And so some percentage of the population is always going to believe that this was handled unfairly, improperly, in a way that disadvantaged Hillary Clinton.

And I think that all of this will be, again, rehashed when Robert Mueller makes his report.

KELSEY SNELL: Yeah, I think that one of the things that we are watching happen here politically speaking is that you are watching people on the campaign trail right now not talking about protecting Mueller - that's not the message Republicans are campaigning on.

The only ones who are talking about Mueller are talking about how it is a witch hunt.

And that - I mean, that further solidifies the idea that there are maybe three core groups of people when it comes to how America views this.

There are the people, like you mentioned, who believe that this - basically, that he's a Russian operative and that this is a big problem, and that Hillary Clinton was wronged.

You have the people who believe that this is a witch hunt.

And then you have a large number of people in America who can't keep track of what's going on.

And the polls, when they - every person that I talk to in the campaign arm of the Democratic Party and the Republican Party say people aren't paying attention to this and they generally have no opinion of this investigation, though they realize that it's probably important.

ROBERT COSTA: So people may not be able to pay attention to it all the time, but the person you can't escape this week is the former New York mayor, Rudy Giuliani.

Yamiche, I feel like you and I have him on speed-dial, calling him every day for our newspaper stories and our reports for PBS NewsHour.

Mr. Giuliani is certainly the TV lawyer that President Trump wanted, someone to hammer the message to the public.

Here are just a few of the statements the former New York mayor made this week.

RUDY GIULIANI: (From video.)

This is a completely tainted investigation.

You get a big liar like Comey, a big liar like McCabe in the FBI, a guy with a conflict of interest from day one on the Hillary investigation.

So it's about time to get the darn things over with.

It's about time to say enough - we've tortured this president enough.

ROBERT COSTA: Yamiche, we've had many interviews with Rudy Giuliani.

You've talked to him.

When is he actually going to make a decision on whether the president will sit down with Robert Mueller for an interview?

YAMICHE ALCINDOR: I think both of us ask him that question every single day.

I asked him that question yesterday and said - ROBERT COSTA: Is he going to do it or not?

YAMICHE ALCINDOR: I don't know.

He doesn't know.

He said that they're - at this point the Mueller team and Trump's lawyers have been in conversations that were narrowing the scope of the questions.

He wasn't very clear when I talked to him about what that really meant and whether or not he could sit down.

I said, so, is he kind of ready to sit down?

He said it's way too soon to say that he's - that he's ready to sit down, this of course being the president.

The thing that Rudy Giuliani is doing is going back and basically feeding this idea that this is all something that was made up and that that the president is this wronged victim, and I think maybe it's working in some ways because I think what you said about this idea that the population is ready to look at it from the lens with - from the lens that they come from from a political party.

I think that the key thing here is that when we say people don't care, you're not talking about Democrats who are still angry that Hillary Clinton lost.

All those people are, like - are looking at Robert Mueller saying please deliver whatever you can to get this man out of office.

And then the Republicans, who feel like so many people told them that they were - that they were supporting the wrong candidate and that President Trump could never win, those people feel very wronged and feel like we should be doing a victory lap, not worrying about this investigation.

ROBERT COSTA: Does Mueller issue a subpoena if Giuliani and the president decline an interview?

MARK LANDLER: Well, he could issue a subpoena.

It's not clear he will because Mueller - he hasn't shown his hand in terms of how aggressive he's willing to be, hence that whole discussion about whether he would indict President Trump.

He tends to play things pretty much by the book.

It's not clear, if he did, how the president would respond.

It would quickly escalate if he rejected it.

I think, just to pick up on the point Yamiche was making, the reason that Rudy Giuliani has to be so careful on this question is that I think that a lot of his lawyers or several other lawyers would argue that there are a lot of risks for him speaking to the special counsel because a lot of the things the president have said to date have been proven wrong or contradictory, and so I think there's a real worry on the part of his legal team to put him in front of Mueller.

ROBERT COSTA: When you talk to people at the DOJ, Devlin, Giuliani asserted this week that the DOJ and Mueller can't charge the president, that it ultimately will end up in the hands of Congress whatever he decides to do.

Is that the Justice Department's standpoint?

DEVLIN BARRETT: Yeah, I think that's actually the most legally solid thing Giuliani has said in a long time.

You know, you talk to lawyers around town and a lot of them are flabbergasted by many of the things he's saying in these interviews in public.

However, on that point there is a general understanding and principle within the Justice Department that a sitting president is not to be indicted.

Now, that hasn't really been tested completely lately, but that is really what the position of the Justice Department is - has been historically, and I don't think Mueller is out to change Justice Department policies.

That's not what Mueller's here for.

I do think that if it comes to it, if it comes to an outright refusal to come in without a subpoena, I do think Mueller's the kind of person who is willing to issue a subpoena.

That obviously raises the stakes, and as you say would probably get fought out in court, could be an intense thing.

ROBERT COSTA: We'll keep an eye out on that report whether he does the interview or not.

But there's been more, actually, news on the Mueller front this week, because one year into the investigation on Capitol Hill the Senate Intelligence Committee - eight Republicans and seven Democrats - concluded the Russians did meddle in the 2016 election and boost Mr. Trump.

And this week the Senate Judiciary Committee released a report on that Trump Tower meeting between Don Trump Jr., Jared Kushner, and Russians that has drawn scrutiny.

And we learned that Mueller has reached a plea deal with the ex-son-in-law of Paul Manafort, Mr. Trump's former campaign chairman.

With all of these moving parts, as we've been discussing, there's been one constant: the secrecy surrounding the whole Mueller operation, no leaks.

Yet, as Kelsey was mentioning, there is a recent CNN poll that finds Republicans are increasingly losing faith in the special counsel; only 17 percent of Republicans have a favorable opinion of Mueller.

That is the case with Republicans, but you do see on Capitol Hill the Senate Republicans, working with Senate Democrats, came to the conclusion that was different than the House Republicans, and they say the Russians did meddle and they did boost Trump.

KELSEY SNELL: Yeah.

If there was ever a week where you saw a stark difference between the Senate and the House approach to this, this week was absolutely it.

You saw Senate Republicans saying things that House Republicans would absolutely never stand behind.

In fact, House Republicans said that - they dismissed the findings that that - that it was - sorry, that the election was tilted towards Trump.

They rejected this entirely.

Now, you see all of the Republicans coming out and saying that they are happy and the Senate Republicans happy to continue looking into this, that they want to continue their investigation.

And the partisanship on the House side is not surprising.

They are drawn into districts where they are more likely to be elected by those Republicans that you're talking about, the people who are more likely to believe in the president.

So they have different political concerns back home and it appears when they are legislating.

ROBERT COSTA: One question, Yamiche, is about the mandate that Mueller has, is he stepping outside of his bounds or not, and Giuliani keeps telling you in his interviews that he doesn't want to - the president doesn't want to talk about Michael Cohen or Stormy Daniels should he sit down.

Is that an issue that the Trump side is going to continue to push?

YAMICHE ALCINDOR: I think that is.

That's why Rudy Giuliani said that they're trying to narrow the scope of the questions.

But the sources that I've talked to who are familiar with how special counsel investigations work are this is why presidents hate them, because they can start getting all these tentacles and start going all these different directions.

And when you have someone like President Trump and all his associates who have so many intertwined and kind of complicated financials, that's how you get into, oh, maybe Michael Cohen's going to somehow come up and connect with Mueller, maybe somehow Stormy Daniels is going to figure - is going to somehow figure into this.

So there's this idea that the president might be very nervous with sitting down.

The other thing I'll say is that the one thing that Giuliani didn't say today and really at all this week is that the president - that the DOJ wouldn't indict the president's - I'm sorry, the president's children.

So you think about Donald Trump Jr., like, he could be indicted.

Jared Kushner could be indicted.

So there's all these people around Donald Trump who are - who could be in legal jeopardy, and that's kind of something that's a lot bigger.

And when I think about President Trump sitting down with the special counsel, I think about that interview that he had with Lester Holt.

We have all these ideas of President Trump not telling the truth, but then when he does tell the truth it could be problematic.

He said, well, why did you - why did you fire Robert - why did you fire James Comey?

Well, it's because of the Russia thing.

And that, to me, was stunning, but it was also him telling the truth.

So if he does go into the interview and tell the truth, what does that mean for his case?

ROBERT COSTA: Speaking of a question mark, Mark, you've studied American power in international diplomacy.

The president's trying to do North Korea, trying to do a lot of things around the world.

What does it mean to have this cloud, as he calls it, around his presidency as he engages in foreign policy?

MARK LANDLER: Well, and it's sort of interesting, the White House continues to function rather normally in terms of the National Security Council and the State Department and the Cabinet.

So at some level the policy continues.

The problem is when you have a president who is this distracted and this preoccupied you can have, you know, the president lose the plot.

There was - I was talking to a White House official a couple of days ago about North Korea policy, which has gotten a bit messy in the last few days.

The North Koreans have sent some strange signals about whether this summit meeting is going to happen or not.

So here is the president dealing with this curveball from the North Koreans at the very moment that he's also so preoccupied with his own legal situation, and I think there's a danger when you have a president that, as Nixon did during Watergate, starts to become so wrapped up in his own issues that he's not thinking clearly about some of these critical problems.

ROBERT COSTA: We'll have to end it there.

Thanks, everybody, for joining us tonight.

Our conversation will continue online on the Washington Week Extra.

We will discuss this week's primary elections.

You can find that later tonight at PBS.org/WashingtonWeek.

I'm Robert Costa.

Thank you for joining us.