Transcript for Dan Abrams on Cohen court filing: 'Biggest legal threat we've seen so far' for Trump

Good morning. And thanks for joining us this Sunday. After a relatively quiet week to honor the nation's 41st president, the last 48 hours have been anything but. The most recent example came yesterday, when president trump confirmed that his chief of staff, John Kelly, would be leaving the white house at year's end. But the biggest news came through court filings Friday from the special counsel and federal prosecutors in New York. The president claims those filings clear him completely. In fact, far from clearing trump, the documents portray potential legal liability that may be far more significant than many had believed. Robert Mueller's case is beginning to demonstrate a pattern of contacts between Russia and trump associates. A series of lies about the extent and nature of the contacts. And a possible financial motive. That sprawling tower trump had long sought in Moscow. What the special counsel called a, quote, lucrative business opportunity that sought and likely required the assistance of the Russian government. And as if the special counsel's probe were not enough, the president faces an entirely separate and growing legal threat. Federal prosecutors working for the department of justice now claiming that then-candidate trump directed illegal hush money to two women during the 2016 campaign. Potentially implicating the president in a federal crime. Which already has a top Democrat saying it could, if true, be grounds for impeachment. And this morning, we'll connect the dots. And get to the bottom of where things stand in these investigations. Let's start with our legal panel. ABC news chief legal analyst Dan Abrams. Former FBI special agent and Yale law lecturer Asha rangappa. And former New Jersey governor, former federal prosecutor, and ABC news contributor Chris Christie. Dan, let me start with you. A lot of different investigations. A lot of strands here. Let's go piece by piece and start with the southern district of New York and its sentencing memo on Michael Cohen. One of the biggest headlines out of that report relates to campaign finance violations that came out of the so-called "Hush money" payments to stormy Daniels and Karen Mcdougall. They note in the report Cohen played a central role in two similar schemes to purchase the rights to the stories. Each from women who claimed to have had an affair with individual 1, so as so suppress the stories and thereby prevent them from affecting the election. The president being, quote, individual 1. So the government appears to directly implicate the president in something that is a federal crime. How much of a legal threat does this pose to the president? I think this is the biggest legal threat we have seen so far. This is not Mueller's team. This is the federal prosecutors, who, in essence, work for Donald Trump in the southern district of New York who filed this sentencing memo, which basically says, we think this crime is really serious. We think it was done intentionally to subvert campaign fitness laws. We think it was done intentionally to affect the election at the coordination, with coordination from and at the direction of Donald Trump. It is the first time where I have seen something in connection with this investigation where I have said to myself, you know what? I think they might actually seek to indict Donald Trump here. That doesn't mean they would seek to try him. But indict him. By implicating him so much this way, and in effect, by name, these prosecutors are making clear, we think this crime is serious and we think he's involved. Governor Christie, if you were still a U.S. Attorney, would you indict the president? Well, first off, it's justice department policy that says you can't indict a president. So, you know, my guess is that I wouldn't. I would follow justice department policy. Now, I agree with Dan that, the language in the sentencing memo is different than what we have heard before. We have heard before from Michael Cohen that he did this in coordination with the president. The only thing that would concern me if I was the president's team this morning is the language. The language sounds very definite. What I would be concerned about is what corroboration do they have? Because everyone knows that Michael Cohen is not going to be the most effective or trustworthy witness on the stand, given some of his past statements. Question is, they sounded very definitive. In my experience, the problem is, when prosecutors are that definitive, they have more than usually just one witness. The flipside for the prosecutors is, they better have more than one witness on this. Because if you're shooting at the president of the united States and the only bullet in your gun is Michael Cohen, then I think that is a problem. I note the same thing Dan did. I have always said that the Michael Cohen situation was much more perilous for the white house than was Bob Mueller. There is no Russian collusion. There's been no proof of Russian collusion. And there doesn't appear to be, I don't think there will be. This is the stuff that's much more -- should be much more concerning to the white house legal team. And that language is very, very strong. Very definitive. The prosecutors better have corroboration. If they don't and they're just going with Michael Cohen, that's a problem. But if they do have corroboration, that could be a problem for the white house. And Asha, do you agree? Felony convictions in campaign finance are not all that common. So what do you think New York prosecutors do now? That's right. I do agree with the governor that the prosecutors would need to show that the president acted knowingly and willingly to commit a criminal violation. Here, with regard to the witnesses. Let's remember that the trump organization CEO. Alan weisselberg, has been talking to prosecutors. I know Rudy Giuliani is comparing this to the John Edwards case. There are differences here. There with witnesses available to corroborate things like the reimbursement made to Michael Cohen. The purpose they were done. Why they were concealed. And you have a tighter, a more direct timing issue here in the sense that these payments were made almost right before the election. And ten years after the affair actually took place. Which tends to substantiate that this was done for the purpose of affecting the election. I believe the prosecutors would have a strong case if they decided to pursue it. I think we all take for granted too much this idea that they definitely can't indict a sitting president. There's a difference between an indictment and a criminal trial. If you actually read the most recent assessment from the office of legal counsel, they seem to be saying you can't indict and prosecute a sitting president. Yes, they talk about the idea of an indictment. But I don't think that's completely off the table, particularly when you read this document. Governor Christie, I want you to jump in. I disagree with Dan on this in this respect. What is your end here? If I were a U.S. Attorney making this judgment, they say, you can indict the president, Chris, but you can't try him. You do that if someone is outside your jurisdiction in a foreign country. Et cetera. But when row have no other way to go. Statute of limitations problem here. The potential of five-year statute of limitations. If the president were to then continue for a second term, it would expire. Here's the issue, though. You have an alternative venue. The alternative venue is the house of representatives. If the house of representatives believes this is a high crime and misdemeanor as defined by the constitution, the house can bring articles of impeachment. Which are the equivalent of an indictment. I argue that that is the way to do this. One other thing I want to point out about willfulness and intent. You know, I think what you'll hear the president argue is that he -- this is the first time that these women, at this juncture, threatened to go public about these alleged affairs. And that he wanted to be kept quiet to avoid the embarrassment for himself and for his family. There is no evidence at this point, that we know of, that they had threatened to go public any time before. But they had gone public before. Stormy Daniels told her story to two magazines and a blog. And she took a polygraph for them. So this has been out there, as far back as 2011. So I think that that argument. I agree with the governor that that's the argument that will be made. But I think that it will be a very hard one to make. I think it will be hard for the president to argue that he's trying to protect his family and business when he's made it part of his brand, really, to be a womanizer who has affairs and leaves previous wives very publicly. This doesn't seem like something he's otherwise tried to keep secret. I don't think that's part of the brand. And I don't think that's what you hear the president or anyone around him argue. In the end, you know, the willfulness and intent portion will be the hardest thing to prove. That's why, Martha, as you rightly said, you don't see a lot of felony prosecutions brought on campaign finance violations. Because that's a pretty high hurdle to cross. Let me move on to the Russia investigation. We have to get to that. There's so much to turn to. Collusion. We have been talking about collusion for many, many, many months. We have from Robert Mueller evidence of a series of contacts between individuals in trump's orbit and the Russians dating back to the early days of the campaign. Those are contacts, not collusion. What more would the special counsel have to show to have collusion, Dan? Well, you still need a crime here, right? I mean, you're allowed to have conversations with Russians. There's no crime against having conversations with Russians. No crime against having conversations with Russians about building a huge tower with Donald Trump's name on it. The question becomes, why did the trump team want to push back the date from June of the conversations about the trump tower back to January? What additional contacts were happening between January and June? And when you read the sentencing memo this one from Mueller, specifically says that he's providing information that goes to the core of the Russia investigation. The core of the Russia investigation. So, that means we're not just talking about conversations with Russians. Again, doesn't necessarily mean they'll find that there was a crime here. But I would be very nervous if you're in the trump orbit with that kind of language coming out of the sentencing. I would be less so. For this reason. You saw how definitive the southern district of New York was. And it's stark that Mueller was not nearly that definitive. Now, that can mean one of two things. He's not ready to be definitive yet. He doesn't have enough evidence. But this has been going on for 18 months. And he had cooperation from manafort and Cohen for some time. Now, he may be making a strategic decision not to lay that card out right now. If I were the trump legal team, I would be focused on the things talked about in the Cohen sentencing memorandum. And not the Mueller sentencing memorandum because it's not as specific or definitive. This is why it's very difficult when people lie to you and you're a prosecutor. It delays the investigation. The fact that manafort was quote/unquote cooperating doesn't really help here. He was lying to them the whole time. I want to disagree with my colleagues. I don't know that there has to be a crime. This is a counterintelligence investigation. That means that collusion can involve agreeing to, they would be still conspiracy to defraud the United States. But trying to help your foreign adversary execute an intelligence operation against the United States is problematic from a constitutional point of view. But where's the evidence of that? I mean there's no evidence. Because Mueller -- the sentencing memos show there were contacts with Russia going back to 2015. That means that with overtures to make a meeting with president trump -- then-candidate trump and Putin. That expands the timeline. That means there was a self-interested motive. Whether it was for the trump tower, the Moscow tower. But whether makes a difference. Depending on which one, it's crime versus not crime. This is where -- Governor Christie, let me ask you this. If manafort's conversations were all legal, why would he lie about them? Is that suggestive of a coverup? Well, because Paul manafort is a consistent liar. And he has been. He's been proven so by Bob Mueller and others. So the fact that Paul manafort is trying to spare himself time in prison is no great shock. I will tell you, as a former U.S. Attorney, the kind of conversation we just had, is why you have a U.S. Attorney. Agents -- FBI agents do an amazing job. They work incredibly hard. They get incredibly invested in their cases. The job of the U.S. Attorney or in this case, special counsel Mueller, will say, okay, what can we prove beyond a reasonable doubt? On Russian collusion we have not seen anything other than there were contacts. As Dan said earlier, if those contacts are about building an office building in Moscow and giving the penthouse to Vladimir Putin, people may not like that. But it's not a crime. We haven't seen the key phrase here. There's a lot redacted. A lot of what we're seeing has big, big black marks over sentences. There's a reason for that. Because Robert Mueller is not ready to disclose what he has. It doesn't mean he doesn't have it. It means he's not ready to discuss it yet publicly. I think that is a critical factor. Governor Christie, one quick question for you to close on. That is the president tweeting that he's totally clear. You disagree with that, I suspect? My view would be that you're not totally clear. Nor is anyone. Until Bob Mueller shuts down his office and hands in the keys. Special counsels can go on for a very long time. This one has. I mean, for goodness sakes. The guy the president just nominated to be U.S. Attorney general appointed a special counsel in 1992 in the middle of the bush re-election campaign that went on for three more years and found no crimes committed by the bush administration. So these things have a life of their own, Martha. So I would say to everybody what I said to the president from the beginning. There is no way you can make it shorter. There's lots of ways to make it longer. One of the ways to do that is to say you're in the clear when the prosecutor still has subpoena authority, the ability to indict people, and the ability to keep the investigation going. Until Bob Mueller shuts down, hands the keys and his credentials back in, he's not in the clear. There's nothing to support that. He's directly implicated. On that note, we'll end it. Thank you governor Christie.

This transcript has been automatically generated and may not be 100% accurate.