Deborah E. Lipstadt, a professor of modern Jewish history at Emory University, is perhaps best known for the libel suit filed against her, in the United Kingdom, by the Holocaust denier David Irving. Lipstadt won the case in 2000. She went on to write a book about it, “History on Trial,” which was the basis of the 2016 film “Denial,” starring Rachel Weisz as Lipstadt. In Lipstadt’s latest book, “Antisemitism: Here and Now,” she examines the recent rise in anti-Semitism in the U.S., the U.K., and Europe. There has been a sharp uptick in hate crimes against Jews, and prominent politicians and heads of state, including Donald Trump and Hungary’s Viktor Orbán, have wooed voters with anti-Semitism (and, perhaps, just expressed their honest opinions).

Lipstadt’s book takes the form of a series of letters between Lipstadt and two fictional characters—a Jewish student and a non-Jewish colleague—whom Lipstadt describes as composites of people she knows who are worried about anti-Semitism. Lipstadt herself is very troubled by its resurgence, and is virulently opposed to both the Trump Administration’s dalliances with anti-Semitism and its embrace of a right-wing government in Israel that seems happy to ally itself with nationalist, anti-Semitic regimes like Orbán’s. At the same time, Lipstadt is worried by what she sees as the “subtle—and sometimes not-so-subtle—antisemitic attitudes and behaviors that one encounters in groups that are connected with progressive causes.”

I recently spoke with Lipstadt by phone. During our conversation, which has been edited and condensed for clarity, we discussed the differences between right-wing and left-wing anti-Semitism, why Israeli leaders are willing to make alliances with anti-Semites, and whether “the negation of Jewish nationhood” is always anti-Semitic.

What, if anything, is different about today’s anti-Semitism?

On some level, it is the same old, same old. The construct is the same, the stereotypes are the same. But I think what is different today is that we’re seeing a perfect storm, in that usually it comes from either the right or the left politically. Today we’re seeing it from the political right and the political left, and we are seeing it particularly—not only, but particularly—in Europe from Islamist extremists, or jihadists, or whatever term you’d like to use.

The other element that makes today different is that we’re living at a time when there are a number of heads of state, and not just our own, who have created an atmosphere which gives comfort to the people who engage in this kind of thing. Whether you’re talking about Viktor Orbán, in Hungary, or the leaders of the P.I.S. Party, in Poland, or the A.F.D., in Germany.

The groups you listed are all right-wing. Do you think it’s worth distinguishing between right-wing and left-wing anti-Semitism, or do you think that they’re arising from similar things, and it’s more helpful to think of them together?

No, we’re not talking about completely different phenomena. They’re the same because they rely on the same stereotypical elements. I know it when I see it. Now, that’s not a sufficient definition, but it’s that way with anti-Semitism. I know it when I see it because these are the elements that are there—something to do with money, something to do with finance, that Jews will do anything and everything, irrespective of whom it harms or displaces or burdens. Both the right and the left share those kinds of stereotypes.

And they also do come from people who feel that somehow things are changing and we’ve got to find someone to blame it on. Were they to blame them on the bicycle riders, everyone would look at them and say, “You’re nuts.” But, whether it’s loss of jobs, whether it’s globalization, whatever it might be, if you blame it on a familiar figure, that makes sense.

Europe and the United States have taken different tacks in the postwar era on hate speech and anti-Semitism, with some European countries making Holocaust denial illegal. And yet we are seeing a rise of this stuff in both the U.S. and Europe. What do you think about the virtues of each approach?

I still am a firm opponent of laws against Holocaust denial. First of all, I’m a pretty fierce advocate of the First Amendment. Having been sued for libel, and having had that in my life for about six years, I’m more than ever. Even though libel is not covered by the First Amendment, [David Irving] wouldn’t have been able to sue me in this country because he was a public figure.

But I also don’t think that these laws are efficacious. Forget the morality—I don’t think they work. I think they turn whatever is being outlawed into forbidden fruit. We saw it in Germany, when “Mein Kampf” was released from the embargo on it a few years ago. People bought it because suddenly it was something they could get ahold of. I just don’t think these laws work. And the third reason I’m opposed to them is I don’t want politicians making a decision on what can and cannot be said. That scares me enormously.

In the book, you write, “The negation of Jewish nationhood is a form of anti-Semitism, if not in intent, then certainly in effect.” Why do you think this is the case? And by “Jewish nationhood” do you mean a state where Jews are a majority, or do you mean a religious state, or both?

No, I certainly don’t mean a religious state. I mean a state where Jews are, as long as they maintain it, a majority, that they . . . You know, it would never be an artificial majority, in other words. “Uh-oh, those other people are multiplying too fast, get rid of them”—never that. But both a democratic state and, it is to be hoped, a state in which Jews are a majority, where the state acknowledges its identity as a Jewish state while giving all minority groups within that state full and equal rights and equal protection. No rights by sufferance or rights by kindness. Rights by rights. And it’s a tricky thing. I am very much a believer that Jews have a legitimate right to a state, and they have to maintain that state, and that state has to be a democratic state.

I acknowledge that—what is it, “foolish consistency is a hobgoblin of small minds and politicians”?—that if someone was opposed to a Jewish state in 1944, in 1945, I wouldn’t have said, “Oh, that’s anti-Semitic.” Never, because that was not the vision in the Jewish community, and there was a real debate. Immediately after the war, there was a consensus in the Jewish community that the Jews should have a state. That consensus came about very quickly when people realized what happened. But [before that] there were Jews who didn’t believe there should be a Jewish state.

But today we’re talking about a state with six million Jews in it. We’re talking about a functioning, existing state. And to people who say, “Well, it shouldn’t be there, it should be done away with, it should be eliminated”—first of all, on a practical level, where are these people going to go? Don’t tell me about a Muslim state with a large Jewish minority, either a one-state solution or Jews going into a neighboring Muslim state, because there is no place that I look, certainly in the Arab world, and even in the non-Arab world, where you see states with religious minorities that live in safety and in peace and are thriving.