Transcript for Alan Dershowitz says Mueller report 'is going to be devastating' for Trump
welcome back to a fateful new chapter for the trump presidency. Over month from now the president will face a democratic house for the first time. In just over a week he'll face a choice, shut down the government over his border wall or punt on that promise once and for all. Dozens of presidential contenders are lining up to take him on in 2020 and what could be most consequential, the next moves from special counsel Robert Mueller. The president has answered some of his final questions. Will Mueller write his final report or take trump to court to force more testimony? Tomorrow we'll learn if Paul manafort is following through on his promise to cooperate in the case. More plea deals are in the works. Mueller may have been silent during the midterms, but his team has been active behind the scenes. Spending dozens of hours with multiple witnesses. So now, aside from trump himself, no single person has more influence over the trump presidency than Robert Mueller. That's where we start this week our legal experts Allan Dershowitz professor at Harvard law school and author of "Impeaching trump" and ABC analyst Dan Abrams. Dan, let's talk about tomorrow's event. Paul manafort appearing for a status hearing. Explain what that means and its significance. He along with the Mueller team requested a ten-day delay. Until president trump delivered his answers. Correct. We don't know what the reason was. Was it because they want to access the extent of the cooperation with manafort? Is it because manafort is going to be a critical witness in a case they haven't announced yet? That's the big question. Is he cooperating so much that they wanted to wait until they could make a public announcement about another indictment where manafort could be involved? Or potentially so little that he could be indicted again. I have no question they're not thinking about using him as a witness. His credibility is shot. Why would they strike a deal with him? They want him to provide information, documentary information, self-proving information, information about events they could follow up. It would be a mistake to use manafort or Corsi or any of these guys who have real credibility problems. Mueller is too smart for that. He's going to have to make an air tight case. Relying on the credibility of admitted liars is not the way to go. If it's uncorroborated. That becomes the key question. They might use someone like manafort if they can back up his account with independent evidence. As a result he could be a critical witness. Allan, they seem to be working hard to make these deals. You mentioned Corsi and that's Jerome Corsi could become a witness against Roger stone. Not a witness. He's a birther. He's a conspiracy theorist. He's not going to be a witness. As a defense attorney, I love when they put on people like Jerome Corsi and manafort. Even when it's corroborated. They're so much better off not putting on the witnesses and using the information to make the case. Let's just talk about information. We're getting information from Paul manafort. We're getting information perhaps from Jerome Corsi. We're getting information from Gates and cone. We're getting information from a lot of people. It is. I think the report is going to be devastating to the president. I know the president's team is working on a response to the report. At some point when the report is made public, that's a very hard question considering the new attorney general who has the authority to decide when and under what circumstance to make it public, it will be made public with a response alongside. The president will say it's political. There's their account and our account. The American public will have toe judge. For you to say it's devastating is something. Let's talk about why Jerome Corsi is important. Some people say Mueller is veering off into all these different areas. Jerome Corsi goes to the heart of the question as to who knew what and when about the hacking, about the distribution of that information et cetera. If they make a deal with someone like Jerome Corsi, that means they believe he's got information linking it back to someone in the trump campaign. Doesn't mean it's Donald Trump himself. Roger stone the most likely. Roger stone the most likely. That's really important on the critical questions we've been talking about. The critical questions are largely political. When I say devastating, I mean, it's going to paint a picture that's devastating. I don't think it's going to make a criminal indication. Collusion is not criminal. Conspiracy to cooperate with an attempt to obstruct the United States government is a crime. That's too much of a stretch. Conspiracy to attempt to obstruct the United States government, they'll need more than that. Mueller is not going to take the chance on being rebutted. He's going to lay out just the facts. Just the facts, ma'am. He'll lay out the fa leave it to congress to decide whether that rises to the level of impeachable offenses. Trump's greatest vulnerabilities do not lie with Mueller. They lie with the southern district of New York. Mueller's allegations have constitutional defenses. If there's any shenanigans having to do with business, they don't have constitutional defense. Allan is saying the president can't obstruct of justice. He can be if he tampers with witnesses and there are other things. Tampering with witnesses could be interpreted broadly. You can't tamper with witnesses with public tweets. You tamper with witnesses by sigh lendly doing what Nixon is by offering them money. What about dangling pardons? That's all public. We don't know it's all public. Where does it say it has to be private? We don't distinguish between public and private. People don't commit crimes in public. I understand that. Where does the law say that? What bush did to Casper Weinberger is identical. Hi par -- he pardoned on the eve of the trial to avoid criminal prosecution. Nobody suggested criminal prosecution here. The difference here would be he's pardoning to protect himself. So was bush. Hoe pardon -- he pardoned to protect himself. The great fear was that Casper Weinberger would point the finger back to him. Let me interrupt with a hypothetical. You bring up Casper Weinberger. Let me bring up a different hypothetical. If Robert Mueller determined that president trump or his team or associates or his agents have in some way suggested to Paul manafort, to Michael Cohen, to Flynn that a pardon would be in the offering if they did not testify to Robert Mueller, that's obstruction isn't it? No. Thomas Jefferson did that in the trial of Aaron Bure. He brought people into the white house and said if you testify favorably I'll give you a pardon. If you don't I'll prosecute. That is not a crime. The problem is what Allan does is isolates an individual issue like a pardon. The issue I think Mueller is going to do is he's going to puzzle this together and say it's not just about pardons or alleged witness tampering. If this happens -- I don't know Mueller is going to have this. If he has it -- I agree that's what he going to do. Together I think even you would have to agree at some point that there is a line which can be crossed. But it wasn't crossed. How do you know it wasn't crossed? We have a pretty good sense from what's been out there about what at least the president is alleged to have done. It would be a foolish mistake for Mueller to take it to the next step and say this is a crime. The other side will be able to rebut it. If he lays it out and leaves it to the American public, that would be wiser. That could be what he does. Final question. Is there anything the acting attorney general, Matt Whitaker, can do to interfere with the mule investigation. Politically it would be a disaster. I think Mueller got everything done before the midterms. He wanted to make sure he was finished with all his work. That's why he accepted the written statements. He didn't want the new attorney general or acting attorney general to be able to interfere. It would be politically a disaster if the new attorney general did that. Mueller could humiliate him in so many different kinds of ways. As Allan pointed out before, this investigation has tentacles in other offices, not just sitting with Robert Mueller. It's something we haven't even discussed. We don't know they're connected to the Mueller investigation. Now more than a dozen sealed indictments in federal district court in Washington, D.C. Those are significant. It's going to be a big week. Thank you both very much.
This transcript has been automatically generated and may not be 100% accurate.