A paradox of 20th-century American politics is that its most sustained ideological movement, modern conservatism, was the brainchild of ex-Communists who had been disillusioned by the crimes of the Soviet revolution or caught on the wrong side of factional disputes. Estranged and unhappy, they went in search of a new god and helped create it—in the mirror image, it has often seemed, of the one that failed them the first time. Together they were “Stalin’s gift to the American Right,” John Patrick Diggins wrote in Up From Communism (1975), his account of four writers who exiled themselves from the left and then wandered like restless spirits before finding refuge in the pages of William F. Buckley Jr.’s National Review in the 1950s and early 1960s.

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In Exit Right: The People Who Left the Left and Reshaped the American Century, Daniel Oppenheimer, a writer and a director of communications at the University of Texas at Austin who was born the year after Diggins’s book came out, reprises and updates the history of political defectors. To Oppenheimer’s credit, his own politics, which seem somewhere on the left, don’t intrude on the absorbing stories he tells. He begins with the ex-Communists Whittaker Chambers and James Burnham, then discusses two renouncers of liberalism, Ronald Reagan and Norman Podhoretz, and closes the circle with two casualties of the ’60s–’70s radical left, David Horowitz and Christopher Hitchens. “The ex-believers—the heretics, the apostates—are the problem children of any politics, in any time,” Oppenheimer writes. But the problem, he suggests, isn’t theirs. It’s ours. So quick to denounce or praise, and to demand to be told which side everyone is on, we forget that politics also offers parables of second thoughts and transformation. Ideological changelings, if we catch them mid-flight, remind us that “belief is complicated, contingent, multi-determined.” They can show us, too, “how hard it is to be a person in the world, period, and how much more confusing that task can become when you take on responsibility for repairing or redeeming it.”

Repairing and redeeming set the bar awfully high, and imply a religious mission. This was true enough for Chambers, the Soviet spy turned impassioned anti-Communist, who really did think of himself as Jonah spat out of the whale: He wrote of his exemplary role, as the accuser in the Alger Hiss spy trial (“the Great Case”), that he had miraculously prevailed “against the powers of the world arrayed almost solidly against” him. But what of the bon vivant Hitchens, who didn’t ever quite leave the left and whose ideological arabesques came in the pages of The Atlantic, Vanity Fair, and The Nation and in what he once described as “the guilty companionship of the green room, where rivals forgather to remove makeup and more or less behave as if they all know they’ll be back sometime next week”?

The differences aren’t lost on Oppenheimer. While in principle his subjects offer a model of political engagement, the character of the apostates changes over the course of his narrative, which spans nearly a century. Put most simply, they become less serious, reflecting a broader decline in America’s ideological life. Chambers was a poète maudit and an acclaimed literary Bolshevik in the 1920s who then slipped underground to supervise a spy ring that eventually infiltrated the State Department. Burnham, his contemporary, was a theorist and a leader of the Socialist Workers Party, a favorite subaltern of Leon Trotsky’s when Trotsky was trying to organize the anti-Stalinist revolt from exile in Mexico.

Ronald Reagan (Lawrence Jackson/AP)

Chambers and Burnham were relatively young men, in their mid-30s, when they gave up the revolution because the facts of the Soviet Union had become too ugly to justify. Their withdrawals were principled, agonized, and ennobling, Oppenheimer argues. Each came away from the experience with important lessons to teach. In addition to his eloquent testimony against Hiss, which amounted to a kind of public seminar on underground Communism, Chambers wrote his great memoir, Witness. A book of power and harrowing beauty, it is evidence, Oppenheimer believes, that Chambers’s “imagination was at its most capacious and subtle only once he had become a conservative.” Burnham wrote two classics of mid-century realpolitik—The Managerial Revolution and The Machiavellians, studies in power and the rise of “elites” (a term he helped popularize)—along with later books on Cold War strategy that were closely read in their day, including by policy makers in the Eisenhower administration.

At the same time, these two men, dissimilar though they were, shared an apocalyptic, even catastrophic, worldview. Chambers notoriously said he had forsaken “the winning side for the losing side,” and Burnham, too, seemed in thrall to the revolutionary vision up to the end. The free world was threatened with extinction, and in its blind optimism seemed to welcome doom, while on every side concealed enemies spun the global “web of subversion,” as Burnham put it, at home and abroad.

This extremism also showed in other ways, which Oppenheimer doesn’t discuss. Chambers’s post-exit period included nearly a decade at Time magazine, where he became Henry Luce’s favorite ideological enforcer, keeping liberal journalists in line during the last stages of World War II, when Cold War tensions were already beginning to surface. Correspondents, including Theodore H. White in China, were shocked to see the facts they had painstakingly gathered in the field fed into Chambers’s newly built anti-Communist thresher.

Along with his geopolitical writings, Burnham produced journalism tinctured with McCarthyism. In his essay “The Case Against Adlai Stevenson,” published in 1952 in The American Mercury, the “case” included a dossier on Stevenson’s adviser Arthur Schlesinger Jr. “Schlesinger is married to the sister of John K. Fairbank, of Harvard,” Burnham wrote.

It would be a cruel thing to hold a man to blame for his brother-in-law. But Schlesinger has taken explicit political as well as personal responsibility for the bona fides of Fairbank—of whom it has been testified under oath that he was a member of the Communist Party.

In fact, as Burnham knew very well, Schlesinger was a New Deal Democrat and a co-founder of Americans for Democratic Action, a liberal organization that emphatically excluded Communists. His sin was not being punitively anti-Communist enough for the ex-Communist Burnham.

Oppenheimer omits all of this because, I think, he wants us to see these early “ex-believers” at their best and register the contrast with later, more openly self-serving and opportunistic figures. Reagan’s apostasy was the first of a new kind, in Oppenheimer’s telling—less a fraught reckoning with the forces of history than a canny repositioning keyed to the changing climate. Never enrolled in the revolution, Reagan was a thriving member of Hollywood’s liberal left and a longtime leader of the Screen Actors Guild, sometimes tangling with labor activists who didn’t grasp, as he did, “the fundamental decency, virtue, and productivity of the American people,” Oppenheimer writes. In the 1950s, while still a Democrat but moving rightward, Reagan closely studied Witness and National Review, whose most august presences were Chambers and Burnham. Reagan combined their teachings with the free-market principles he espoused as a spokesman for General Electric. The result was his uniquely sunny brand of conservative homiletics, which sounded hopeful even when it included dark warnings that Medicare was the first step toward serfdom and would lead to “other federal programs that will invade every area of freedom as we have known it in this country until one day … we will wake to find that we have socialism.” Reagan had an outsize ability, Oppenheimer argues, to “discern the simple truth beneath the surface complexity.”

David Horowitz (Wally Fong/AP)

This may sound patronizing. But apostates often cast themselves as pilgrims who have traveled the long, arduous route toward purifying simplicity. Chambers certainly did. So did the ultrasophisticated Podhoretz, a brilliant editor and an accomplished literary critic. “Clarity is courage,” he told Oppenheimer in an interview for Exit Right. “Everything was simple” once he realized he was a conservative after all. “There was nothing esoteric. There was a simple truth behind everything.” This reversed the teachings of his mentor Lionel Trilling, who had himself flirted with radicalism in the 1930s but had come to distrust “the haunted air” of ideology, whether of the left or the right. An English professor at Columbia University, Trilling was the oracle of moral “complexity” and “difficulty”; his own prose exuded nuance and dialectical finesse. He was dismayed when Podhoretz, as the editor of Commentary, promoted radical anarchists like Paul Goodman, and was dismayed again when he read the manuscript of Podhoretz’s memoir Making It (1967), with its candid self-celebration and its picture of social climbing within the “family” of Manhattan intellectuals. Trilling advised Podhoretz not to publish it, predicting that it would be ruthlessly panned and Podhoretz’s reputation would suffer. He was right. Only later, plunged into anguish, did Podhoretz reinterpret the attacks on his book as being covertly, but profoundly, political. His social scorekeeping and odes to success weren’t mere lapses of taste. They were an embrace, however tentative, of “middle-class American values,” and so were a threat to the “radical party line” followed by Manhattan’s literary snobs.

In the space of a generation, from the late 1930s to the late 1960s, we have gone from a revolutionary whose decision to quit the Communist underground involved long months of hiding from possible assassins, to a fixture at Manhattan after-parties whose dark night of the soul began with unfriendly book reviews and being dropped from Jackie Kennedy’s guest list. And the descent continues, as the personal doesn’t just merge with the political but swallows it whole, and as ideological heresy becomes its own form of postmodern exhibitionism. This brings us to David Horowitz, the former Berkeley radical and Ramparts editor whose disenchantment with Bay Area leftism has yielded a franchise that includes the series Black Book of the American Left—volume eight, The Left in Power (From Clinton to Obama), is due out in September—along with varied digital projects. Horowitz runs FrontPage Magazine (“Rename the Racist Democratic Party” is a typical feature), the online journal of the David Horowitz Freedom Center, a Web site whose services include listing college campuses friendly to anti-Israel “terrorists.”

Christopher Hitchens (Chad Rachman/AP)

Exit Right ends with a sympathetic but unsparing portrait of the “professional apostate” Christopher Hitchens, who bounded from one crusade to the next. His ardent support for the Iraq invasion in 2003 forced him into awkward collusion with neoconservatives (Podhoretz, for one) whom he had once reviled, and then into hectoring denunciations of critics of the Bush administration even as the war turned bad and the only defenses he could muster were against “the weakest arguments made by the silliest people,” in Oppenheimer’s estimation.

But Chambers and Burnham stumbled too, and had long histories of misaimed and mistimed zeal. What unites these apostates, in any case, isn’t their life experiences, each unlike the others’, but the death-struggle atmosphere they brought to politics. Even the genial Reagan favored steamy rhetoric: His “evil empire” is the cartoon version of “the focus of concentrated evil of our time,” as Chambers called Communism in Witness. Similar formulations are back in vogue today on the right—in the hothouse catchphrases radical Islamic terrorism and clash of civilizations, and in the casual assertion that President Obama’s policies are transparent appeasements that have “betrayed” the nation.

This is the tone of fanaticism—or, perhaps, “the fanatical style,” a variation on what Richard Hofstadter called “the paranoid style.” Hofstadter was careful to say he was describing not a clinical condition, but a constructed outlook. Its conspiratorial themes grew out of a particular “way of seeing the world and of expressing oneself.” So, too, with the current style of conservative discourse. It assumes the presence of concealed enemies, but also stresses, even more than the “paranoiacs” did, the bad faith of liberals who are unwilling and possibly unable to acknowledge how dire things really are—or to call evil by its true name.

A telling moment in the recent history of apostasy came in 1999, when Hitchens, all but maddened with hatred of Bill Clinton and giddy with impeachment fever, swore out an affidavit against the Clinton loyalist Sidney Blumenthal, implicating him in the president’s alleged crimes. Hitchens and Blumenthal were old friends, quite like Chambers and Hiss, as many noted at the time. Hitchens himself (cast as Chambers) was delighted by the comparison and its “heroic exaggeration.” In fact, it showed how the stakes had changed. The “tragedy of history,” in Chambers’s famous phrase, spoken during congressional hearings, had been cheapened into sex farce.

Back in 1948, Chambers’s accusations against Hiss struck many as unseemly, the ratting-out of a friend, and some suspected hidden motives. At one point, the junior House member leading the investigation, a 35-year-old Richard Nixon, asked Chambers what reason he might have for accusing Hiss. Did he bear him a grudge? “I have testified against him with remorse and pity,” Chambers said, but “so help me God, I could not do otherwise.” Remorse and pity are words seldom used in politics today. But they had meaning for the original apostates, who recognized that blame began with themselves, even if it didn’t always end there.