This weekend, he’s defending Trump. But first Alan Dershowitz wants to defend himself. The “worst thing” to happen to him, he says, was meeting Jeffrey Epstein, which led to Virginia Giuffre’s accusation of sexual assault—completely false, he maintains—a legal battle with her lawyer David Boies, and near-cancelling in some quarters. And the threats he’s received lately for defending the president are worse than when he represented O.J. Simpson in the trial of last century. Now, as he prepares to address a jury of senators, the TV-friendly lawyer insists it’ll be a “very serious” and “somber” affair.

Vanity Fair: Are you ready for all of this?

Alan Dershowitz: I’m taking my head out of the dusty books. I’ve been sneezing from spending the last week in these busy books from the 18th and 19th century. Blackstone’s Commentary. Russell on Crime. The Federalist Papers. I’ve been studying every possible relevant document—the impeachment of Andrew Jackson and the papers on that. I’ve been totally immersed, which is interesting. I’m doing all this research. I’m doing it in good faith. I’m trying to present the Senate with the best research I can. And in 55 years, I have never experienced lawyers personally attacking me with ad hominem. I remember very vividly 65 years ago in the McCarthy era, I experienced it. Since the McCarthy period, I have never experienced such personal, ad hominem attacks and hostility, questioning my integrity and my motives, saying I’m too old. It’s been front-on, McCarthy-ite attacks by supporters of impeachment.

What do you think accounts for that? This isn’t the first controversial thing you’ve done, by a mile.

It’s not even close to O.J. Because we live in the most divided country, even more than the Vietnam War. I was occasionally called disloyal or unpatriotic. But this time I’ve had my family threatened—someone sent me an email with pictures of my family. I’ve been threatened with disbarment. Larry Tribe has said my arguments shouldn’t be listened to, that they’re bonkers. I’m making the same arguments as Justice Benjamin Curtis made in the trial of Andrew Johnson, and yet people are attacking my integrity and my competence. Others have said I’m not really a constitutional lawyer. I taught constitutional criminal procedure for 50 years at Harvard. I’ve written five books on the Constitution, over 25 articles. I’ve litigated over 100 cases on the Constitution. If I were arguing for impeachment, none of them would be questioning my competence or credentials. It’s all partisan hypocrisy.

Are you hardened by the fact that you’re getting attacked? Does it make you want to do it more?

Sure. Of course. It makes it clear that I made the right choice even though I got a lot of objection, including my wife, who was very concerned. She said she would rather see me remain nonpartisan, and neutral, objective and independent. She actually discussed that with the president. They had an exchange of views on it. In the end, we collectively made a decision that I present the constitutional issues, and I think I can present them in a way that hasn’t been presented before. I think it could be useful to the Senate.

What was the exchange like with your wife and the president?

I was supposed to have dinner with a friend, and he said we are having dinner at Mar-a-Lago on the night before Christmas—Christmas Eve, whatever it’s called—would you like to join us? We went up to Palm Beach. We live in Miami for the winter. We were warned that the president would be there, but he was way on the other side of the room. The ballroom is enormous. But then I got online for the buffet, and I was surprised that the president got in line behind me. You would think that the president would be served. I actually offered him my empty plate, but he said no, it was okay, that he’d get his own. Then we started talking, and he asked me if I was willing to do this. We had had conversations before and I hadn’t made up my mind. I said, well, my wife is concerned. He said to bring her over. So I brought over my wife, who, like me, voted for Hillary Clinton. We consider ourselves friends of Hillary Clinton from Martha’s Vineyard. She came over and explained, very cogently, why she thought me being nonpartisan and independent was better. He said that’s a very thoughtful, good idea. You should do what’s best, but a lot of people want to argue this. I want Alan to do it because he would make the most compelling constitutional argument. After the conversation, Caroline and I talked, and we decided I would make the argument on constitutional grounds, but I wouldn’t be involved in the factual issues. It’s what I’ve done on many issues. It’s what I did in the O.J. case. I wasn’t involved in the day-to-day strategic issues. I came in to argue the legal and constitutional issues. I’ve done that on a number of cases, coming in on a special basis. I enjoy that role.