hilip Roth's new novel, ''The Plot Against America,'' which will be published by Houghton Mifflin next month, imagines an America in which the 1940 presidential election resulted not in a third term for Franklin D. Roosevelt but in a victory for a Republican ticket headed by Charles A. Lindbergh. The Book Review asked Roth to write an essay about his new book and how he came to write it.

IN December of 2000, I was reading the bound proofs of Arthur Schlesinger's autobiography and found myself especially interested in his description of the events of the late 1930's and early 1940's as they impinged on his life as a young man traveling in Europe and then back in Cambridge, Mass. They had impinged on my life, too, though I was only a small child at the time. The great world came into our house every day through the news reports on the radio that my father listened to regularly and the newspapers that he brought home with him at the end of the day and through his conversations with friends and family and their tremendous concern for what was going on in Europe and here in America. Even before I started school, I already knew something about Nazi anti-Semitism and about the American anti-Semitism that was being stoked, one way or another, by eminent figures like Henry Ford and Charles Lindbergh, who, in those years, along with movie stars like Chaplin and Valentino, were among the most famous international celebrities of the century. The combustion-engine genius Ford and the aeronautical ace Lindbergh -- and our nation's anti-Semitic propaganda minister, the radio priest Father Charles Coughlin -- were anathema to my father as well as to his circle of friends. Out of choice, virtually nobody in our Jewish neighborhood owned a Ford automobile, despite its being the most popular car in the country.

I came upon a sentence in which Schlesinger notes that there were some Republican isolationists who wanted to run Lindbergh for president in 1940. That's all there was, that one sentence with its reference to Lindbergh and to a fact about him I'd not known. It made me think, ''What if they had?'' and I wrote the question in the margin. Between writing down that question and the fully evolved book there were three years of work, but that's how the idea came to me.

To tell the story of Lindbergh's presidency from the point of view of my own family was a spontaneous choice. To alter the historical reality by making Lindbergh America's 33rd president while keeping everything else as close to factual truth as I could -- that was the job as I saw it. I wanted to make the atmosphere of the times genuine, to present a reality as authentically American as the reality in Schlesinger's book, even if, unlike him, I was giving to history a turn it had not taken.

It also gave me an opportunity to bring my parents back from the grave and restore them to what they were at the height of their powers in their late 30's -- my father, with all the vast energy he was able to pour into what I call his ''reforming instincts,'' and my mother ''performing each day in methodical opposition to life's unruly flux'' -- and then to go ahead to imagine how they might have conducted themselves under the enormous pressure of a Jewish crisis such as they never really had to encounter as native-born New Jerseyans, living all their lives, luckily enough, without an Aryan white supremacist in the White House. I've tried to portray them here as faithfully as I could -- as though I were, in fact, writing nonfiction. My brother I've portrayed less faithfully. I had to manipulate him a bit for the sake of the story. When he read the finished manuscript, he slyly told me, ''You've made me more interesting than I was.'' Maybe, maybe not, but as a brother five years my senior who could draw wonderfully, who could jitterbug, who was very handsome and seemed, at least to his kid brother, to have a way with the girls, he did indeed loom over me in the awe-inspiring way I describe.

The writing, then, put me in touch with my dead parents no less than with the period, and in touch eventually with the kind of little boy I myself was, because I've tried to portray him faithfully too. But the deepest reward in the writing and what lends the story its pathos wasn't the resurrection of my family circa 1941 but the invention of the family downstairs, of the tragic Wishnows, on whom the full brunt of the anti-Semitism falls -- the invention particularly of the Wishnows' little boy, Seldon, that nice, lonely little kid in your class whom you run away from when you're yourself a kid because he demands to be befriended by you in ways that another child cannot stand. He's the responsibility that you can't get rid of. The more you want to get rid of him, the less you can, and the less you can, the more you want to get rid of him. And that the little Roth child wants to get rid of him is what leads to the tragedy of the book.

I had no literary models for reimagining the historical past. I was familiar with books that imagined a historical future, notably ''1984,'' but much as I admire ''1984,'' I didn't bother to reread it. In ''1984'' -- written in 1948 and published a year later -- Orwell presupposes a gigantic historical catastrophe that renders his world unrecognizable. There were 20th-century models for such catastrophes in both Hitler's Germany and Stalin's Russia. But my talent isn't for imagining events on the grand scale. I imagined something small, really, small enough to be credible, I hoped, that could easily have happened in an American presidential election in 1940, when the country was angrily divided between the Republican isolationists, who, not without reason, wanted no part of a second European war -- and who probably represented a slight majority of the populace -- and the Democratic interventionists, who didn't necessarily want to go to war either but who believed that Hitler had to be stopped before he invaded and conquered England and Europe was entirely fascist and totally his. Willkie wasn't the Republican to beat Roosevelt in 1940 because Willkie was an interventionist himself. But if Lindbergh had run? With that boyish manly aura of his? With all that glamour and celebrity, with his being virtually the first great American hero to delight America's emerging entertainment society? And with his unshakeable isolationist convictions that committed him to keeping our country out of this horrible war? I don't think it's far-fetched to imagine the election outcome as I do in the book, to imagine Lindbergh's depriving Roosevelt of a third term. It was far-fetched for Orwell to imagine the world as he did, but he knew that. His book wasn't a prophecy. It was a futuristic horror story containing, of course, a political warning. Orwell imagined a huge change in the future with horrendous consequences for everyone; I tried to imagine a small change in the past with horrendous consequences for a relative few. He imagined a dystopia, I imagined a uchronia.

Why did I choose Lindbergh? As I said, it wasn't far-fetched to imagine him running and winning. But Lindbergh also chose himself as the leading political figure in a novel where I wanted America's Jews to feel the pressure of a genuine anti-Semitic threat. Lindbergh as a social force was distinguished not solely by his isolationism but by his racist attitude toward Jews -- an attitude that is reflected unambiguously in his speeches, diaries and letters. He was at heart a white supremacist, and, leaving aside his friendship with individual Jews like Harry Guggenheim, he did not consider Jews, taken as a group, the genetic, moral or cultural equals of Nordic white men like himself and did not consider them desirable American citizens other than in very small numbers. None of this means that as president he might have turned on the Jews and persecuted them openly, but then he doesn't do that in my book either. What matters in my book isn't what he does (which is very little, once he's signed a nonaggression pact with Hitler only weeks after taking office and allowed for a Nazi embassy in Washington and, about a year later, with his wife, hosted a state dinner for von Ribbentrop, Hitler's foreign minister) but what American Jews suspect, rightly or wrongly, that he might be capable of doing given his public utterances, most specifically his vilification of the Jews, in a nationwide radio address, as alien warmongers indifferent to America's interests. He gave this speech on Sept. 11, 1941, in Des Moines at an America First rally; in my book I move the speech back to the previous year, but I don't alter its content or impact.

At the center of this story is a child, myself at 7, 8 and 9 years of age. The story is narrated by me as an adult looking back 60-odd years at the experience of that child's family during the Lindbergh presidency, but nonetheless a child plays a role in this book comparable to the role generally played by adults in my other books.

During the early months of writing, I found it constraining to be looking at this calamity over the shoulder of a child. It took several months of trial and error before I figured out how to let the boy be a boy while at the same time introducing through the adult's voice a mediating intelligence. The storytelling is very direct in this book, and I tried to keep both the boy's perspective and the adult's perspective from overwhelming the events. I had also somehow to make the two one, the mediating intelligence that sees the general, and the child's brain that degeneralizes the general, that cannot see outside the child's own life and that reality never impresses in general terms. Whereas his father struggles with his America falling apart and the terrible invasion of history, the boy is still living in the heroic America of his stamp collection and, indeed, tries to escape history by running away from home to a Christian orphanage. He is a practical child in a turbulent time, his world made of concrete and immediate fears.

Another problem was to keep the adult's narrating voice explicit without its sounding didactic in recounting the imaginary historical events. After all, my reader can't know anything of the history I'm inventing, there is no common knowledge that is complete, and so, though one can allude to Munich or to the Treaty of Versailles, one cannot allude to the Iceland Understanding (the 1941 nonaggression pact signed in Reykjavik by Lindbergh and Hitler) without spelling it out.

There are four boys who figure strongly in the action of this book, one of whom -- the boy downstairs, Seldon Wishnow -- isn't merely, like the younger Roth child, a 9-year-old confronted by too many problems but the book's most tragic figure, a trusting American kid who suffers something like the European Jewish experience. He is not the child who survives the confusion to tell the tale but the one whose childhood is destroyed by it. It's the children in the book who join the trivial to the tragic; far from constraining me, their presence was what allowed me my latitude.

I chose Walter Winchell to lead the political opposition to Lindbergh because, to begin with, the real Walter Winchell hated Lindbergh and along with people like the columnist Dorothy Thompson and Roosevelt's interior secretary, Harold Ickes, attacked him as pro-Nazi from the moment he became the voice of the America First version of nonintervention. Needless to say, Winchell was never a candidate for president, as I have him being in my book. But then neither did Lindbergh become president. I chose Winchell to lead the political opposition because Winchell was the outsize social creature he was -- as Mayor La Guardia says in his eulogy over Winchell's body (in this book only), ''Walter is too loud, Walter talks too fast, Walter says too much, and yet, by comparison, Walter's vulgarity is something great, and Lindbergh's decorum is hideous.''

What it comes down to is that I wanted Lindbergh opposed not by a saint but by a gossip columnist, the most famous gossip columnist in the country, gross and cheap without apology, whose enemies considered him a loudmouth Jew. Winchell was to gossip what Lindbergh was to flight: the record-breaking pioneer.

The book began inadvertently, as a thought experiment. I had no such book in mind nor was it a book of a kind I was looking to write. The subject, let alone the method, would never have occurred to me on its own. I frequently write about things that didn't happen, but never about history that didn't happen. The American triumph is that despite the institutionalized anti-Semitic discrimination of the Protestant hierarchy at that time, despite the virulent Jew hatred of the German-American Bund and the Christian Front, despite the repellent Christian supremacy preached by Henry Ford and Father Coughlin and the Rev. Gerald L. K. Smith, despite the casual distaste for Jews expressed by journalists like Westbrook Pegler and Fulton Lewis, despite the blindly self-loving Aryan anti-Semitism of Lindbergh himself, it didn't happen here. Though a lot of things that didn't happen here did happen elsewhere. The ''what if'' in America was somebody else's reality. All I do is defatalize the past -- if such a word exists -- showing how it might have been different and might have happened here.

Why it didn't happen is another book, one about how lucky we Americans are. I can only repeat that in the 30's there were many of the seeds for its happening here, but it didn't. And the Jews here became what they became because it didn't. All the things that tormented them in Europe never approached European proportions here. Nor is my point that this can happen and will happen; rather, it's that at the moment when it should have happened, it did not happen. ''The Plot Against America'' is an exercise in historical imagination. But history has the final say. And history did it otherwise.

There was exclusion in America, to be sure. Jews were deliberately and systematically excluded from partaking of certain advantages and making certain affiliations and entering important portals at every level of American society, and exclusion is a primary form of humiliation, and humiliation is crippling -- it does terrible injury to people, it twists them, it deforms them, as every American minority can attest and as the best American minority writers make clear in their work (all too clear for the comfort of the minority boosters who babble on about ''pride''). In this book it's the humiliation that helps to tear apart and very nearly disable the family, inasmuch as each person in the family responds to it differently. What is it to be a man, to be a woman, to be a child, and not be humiliated? How do you try to remain strong when you are not welcome?

Some readers are going to want to take this book as a roman a clef to the present moment in America. That would be a mistake. I set out to do exactly what I've done: reconstruct the years 1940-42 as they might have been if Lindbergh, instead of Roosevelt, had been elected president in the 1940 election. I am not pretending to be interested in those two years -- I am interested in those two years. They were turbulent in America because they were catastrophic in Europe. My every imaginative effort was directed toward making the effect of that reality as strong as I could, and not so as to illuminate the present through the past but to illuminate the past through the past. I wanted my family to be up against it precisely as they would have been up against it had history turned out as I've skewed it in this book and they were overpowered by the forces I have arrayed against them. Forces arrayed against them then, not now.

Kafka's books played a strong role in the imagination of the Czech writers who were opposing the Russians' puppet government in Communist Czechoslovakia in the 1960's and 1970's, a phenomenon that alarmed the government and caused it to prohibit the sale and discussion of his books and to remove them from the library shelves. Obviously, it wasn't to inspire those future writers or to intimidate their future rulers that Kafka wrote ''The Trial'' and ''The Castle'' in the early years of the 20th century. Literature is put to all kinds of uses, public and private, but one oughtn't to confuse those uses with the hard-won reality that an author has succeeded in realizing in a work of art. Those writers in Prague, by the way, were well aware that they were willfully violating the integrity of Kafka's implacable imagination, though they went ahead nonetheless -- and with all their might -- to exploit his books to serve a political purpose during a horrible national crisis.

The book has a postscript of 27 closely printed pages of historical and biographical information -- what I call the''true chronology'' of those years. No other book of mine carries behind it anything resembling this caboose, but I felt obliged here to recognize where authentic lives and events are clearly bent to my fictional purposes. I don't want any confusion in the mind of the reader about where historical fact ends and historical imagining begins, and so, in the postscript, I give a brief survey of that era as it really was. I want to make clear that I haven't dragged real historical figures bearing their own names into my story by attributing points of view to them gratuitously or by forcing them to behave implausibly -- unexpectedly, surprisingly, beautifully, shockingly, but not implausibly. Charles Lindbergh, Anne Morrow Lindbergh, Henry Ford, Mayor La Guardia, Walter Winchell, F.D.R., Montana Senator Burton Wheeler, Interior Secretary Harold Ickes, Newark gangster Longy Zwillman, Newark rabbi Joachim Prinz -- I for one had to believe that, in the circumstances I imagine, each might well have done or said something very like what I have him or her doing or saying; otherwise I couldn't have written the book. I present 27 pages of the documentary evidence that underpins a historical unreality of 362 pages in the hope of establishing the book as something other than fabulous.

History claims everybody, whether they know it or not and whether they like it or not. In recent books, including this new one, I take that simple fact of life and magnify it through the lens of critical moments I've lived through as a 20th-century American. I was born in 1933, the year Hitler came to power and F.D.R. was first inaugurated as president and Fiorello La Guardia was elected mayor of New York and Meyer Ellenstein became the mayor of Newark, my city's first and only Jewish mayor. As a small child I heard on our living room radio the voices of Nazi Germany's Fuhrer and America's Father Coughlin delivering their anti-Semitic rants. Fighting and winning the Second World War was the great national preoccupation from December 1941 to August 1945, the heart of my grade school years. The cold war and the anti-Communist crusade overshadowed my high school and college years as did the uncovering of the monstrous truth of the Holocaust and the beginning of the terror of the atomic era. The Korean War ended shortly before I was drafted into the Army, and the Vietnam War and the domestic upheaval it fomented -- along with the assassinations of American political leaders -- clamored for my attention every day throughout my 30's.

And now Aristophanes, who surely must be God, has given us George W. Bush, a man unfit to run a hardware store let alone a nation like this one, and who has merely reaffirmed for me the maxim that informed the writing of all these books and that makes our lives as Americans as precarious as anyone else's: all the assurances are provisional, even here in a 200-year-old democracy. We are ambushed, even as free Americans in a powerful republic armed to the teeth, by the unpredictability that is history. May I conclude with a quotation from my book? ''Turned wrong way round, the relentless unforeseen was what we schoolchildren studied as 'History,' harmless history, where everything unexpected in its own time is chronicled on the page as inevitable. The terror of the unforeseen is what the science of history hides, turning a disaster into an epic.''

In writing these books I've tried to turn the epic back into the disaster as it was suffered without foreknowledge, without preparation, by people whose American expectations, though neither innocent nor delusional, were for something very different from what they got.