Ben Rhodes,a speechwriter for Barack Obama and, from 2009 to 2017, a deputy national security adviser, is among the former president’s fiercest defenders. In 2018 he published a White House memoir, titled with characteristic certitude “The World as It Is,” in which he first took up the question that haunts Mr. Obama’s legacy: If he was the wonderful president his admirers say he was, why did the country elect Donald Trump to succeed him? Mr. Rhodes’s answer—I will put it almost as plainly as he does—is that Republicans are racists and thus demonized Mr. Obama as un-American, and the country fell for it.

Mr. Rhodes offers that same interpretation in “After the Fall: Being American in the World We’ve Made.” But in this book he expands his brief by portraying Mr. Trump’s election as part of a much wider embrace of nationalist authoritarianism. China’s lurch toward surveillance-state totalitarianism, Hungary’s transition to illiberal democracy, Russia’s reversion to its former status as a global menace—these are all, according to Mr. Rhodes, symptoms of the “virus” that gave us the Trump presidency.

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Political views aside, the book is not a pleasure to read. Mr. Rhodes often writes in a flurry of ill-defined abstractions. “Our own collective embrace of a blend of capitalism, militarism, and technology that somehow bred identity-based polarization” is a typical phrase. He refers casually to the “poorly regulated global economy,” making me wonder when the global economy was well regulated. The meaning of the words “capitalism is as fungible as Communism” eludes me.

But “After the Fall” is, in its way, instructive. “I’ve written thousands of speeches for Barack Obama,” Mr. Rhodes modestly informs us, and he probably understands the 44th president as well as anyone. The problem is that he has none of Mr. Obama’s warmth and personal appeal but all of his self-importance, hypersensitivity to criticism and penchant for highfalutin platitudes.

Rarely has a writer thought more of himself and with less justification. He interviews Alexei Navalny mainly, it seems, in order to compare himself to the Russian dissident—a man who has been harassed, imprisoned and poisoned for his opposition to Vladimir Putin. Though generously allowing that Mr. Navalny’s sufferings “are far greater than anything I have experienced,” Mr. Rhodes sees in him someone just like himself: “a guy who didn’t expect to be doing what he was doing, who was motivated by anger and yet still energized by the whole experience.” Later he speaks with a pro-democracy protester in Hong Kong who describes for him the ways in which the Chinese Communist Party frightens critics of Beijing into silence. This reminds Mr. Rhodes of “the warnings I got at times to tone down my anti-Trump commentary for fear of appearing hysterical, unserious.”

A man who consistently equates opposition to his views with racism and mendacity isn’t likely to notice weaknesses in his arguments, and Mr. Rhodes doesn’t. He laments the Chinese government’s belligerent online censorship of dissenting political opinions but says nothing, for example, about American social-media platforms erasing reasonable assertions by respected professionals that don’t align with the progressive orthodoxy of the moment.

Mr. Rhodes repeatedly describes conservative and “nationalist” political viewpoints he doesn’t like as “grievance-fueled” and “grievance-based,” but he doesn’t bother to mention the obvious counterclaim—even to reject it—that the American left has cultivated racial, ethnic and sexual grievances for so long that we now have a name for them: identity politics.

Occasionally you wonder if he’s pulling your leg. In a long chapter on the evils of Viktor Orbán, the Hungarian prime minister—the left’s current obsession with Hungary, of all places, is on full display here—Mr. Rhodes inveighs against Orbán-linked groups that demonize the progressive Hungarian financier George Soros. Now I am aware that a lot of right-wingers in the U.S. entertain some outlandish theories about Mr. Soros’s influence, although characterizing him, as Mr. Rhodes does, as a disinterested crusader for good government who has “established foundations that give grants to civil society organizations” is a bit much. Mr. Soros is a leftist mega-donor, full-stop. But that’s not the funny part. Four pages later, Mr. Rhodes attributes the Tea Party’s success in the 2010 midterm elections in part to “Charles and David Koch, two billionaires who were among the Republican Party’s largest donors, and their innocuously named organization Americans for Prosperity.” Self-awareness is not the man’s strong point.

Mr. Rhodes believes that progressives are an oppressed and threatened population. Many political-class progressives believe this, for reasons I wish I understood. The left’s values prevail in universities, public schools, newsrooms, corporate boardrooms, cultural institutions, government agencies, and lately the U.S. military.

This strange conviction enables the author of a White House memoir to think of himself and his political allies as objects of censorship and persecution. In a chapter titled “Power Doesn’t Give Up Without a Fight”—an Obama tagline—Mr. Rhodes addresses the point directly. “Even after we were ensconced in the White House,” he recalls of 2009, “power never really did give up.” The “wealthy business elite,” the “military and foreign policy establishment,” and “America’s oil-rich allies in the Gulf,” he reflects, “never took to Obama.” And of course Republicans “relentlessly attacked and sought to undermine Obama, even though he came into office determined to work with them.” So, Mr. Rhodes concludes in a dramatic imperative, “don’t tell me Trump isn’t the establishment.” The claim that Donald Trump was part of Washington’s establishment, whatever Mr. Rhodes means by that term, is so stupidly tendentious that I have to assume he doesn’t mean it.

Elsewhere in the book Mr. Rhodes describes what it was like to be a young speechwriter on the 2008 Obama campaign—“the villains in the story,” he recalls, “were . . . the warmongers, torturers, racists, climate deniers, special interests, and amoral wealthy who always tried to stand in the way of progress”—so forgive me if I remain skeptical of his claim that Mr. Obama “came into office determined to work with” the opposition. It’s true that Mr. Obama inspired hostility. But how could he not, when Ben Rhodes was his muse?