Joe Biden needn’t worry too much, perhaps. Mr. Siegel, 75, has only twice backed a winning presidential candidate since he reached voting age. But while he’s no bellwether, he does make an energetic case for the incumbent.

Mr. Siegel, a professor emeritus at New York’s Cooper Union and a senior fellow at the Manhattan Institute, says he overcame his distaste for Mr. Trump for three reasons. First, foreign policy: “Crushing ISIS, pulling us out of the Iran nuclear deal, moving our embassy to Jerusalem, and making fools of those people who insist that the Palestinian issue is at the heart of the Arab-Israeli conflict.” Second, by his “ability to withstand a prolonged coup attempt by the Democrats and the media,” which started with the Steele dossier: “If I’m saying what I find impressive about Trump, it’s that he’s survived. He has an extraordinary amount of arrogance, egotism, and self-confidence.”

Mr. Siegel’s third reason goes to the heart of his own political philosophy. He sees the president as a champion of “bourgeois values,” under threat from the “clerisy,” Mr. Siegel’s word for the dominant elites who “despise” those values. He regards Mr. Biden as a “captive” of this clerisy, and running mate Kamala Harris as the “embodiment of it.”

“I don’t want to see her as president,” Mr. Siegel says of Sen. Harris. “I don’t want a San Francisco Democrat who’s likely to impose elements of the Green New Deal, which she sponsored but lied about sponsoring on television. If Biden wins, she will be president in short order. I don’t know how long Biden will last.”

In Mr. Siegel’s view, “hard work, faith, family and autonomy” have enabled America to thrive, and Mr. Trump stands for these values, even if he doesn’t always exemplify them. “The elite is largely detached from the middle class,” Mr. Siegel says. “The two major sources of wealth in the last 20 years have been finance and Silicon Valley. Neither of them has much connection to middle-class America, or Middle America.” Mr. Trump is “in favor of manufacturing jobs, which are often middle-class.” The president also “recognizes the ways in which China is a threat to the survival of middle-class life in America, directly and indirectly.”

Mr. Siegel takes heart from Mr. Trump’s hostility to political correctness. “Wokeness is a force that undermines the middle class,” he says, “and you couldn’t have had wokeness without an elite contempt for the values of the middle class.” Middle Americans see political correctness “as a threat to the democratic republic they grew up in, where people could speak their mind.” I ask Mr. Siegel to define political correctness: “The inability to speak the truth about the obvious.”

As we sit on his porch in the Brooklyn neighborhood of Ditmas Park, his opinions—unfashionable in a borough where Mrs. Clinton outpolled Mr. Trump by more than 60 points—cause passersby to turn their heads. When he offers examples of political correctness that annoy him, a young man walking by the house looks startled. “Why can’t you say ‘Wuhan virus’?” Mr. Siegel exclaims. “Why can’t you say there are two genders?” The young man scuttles past as if singed, and Mr. Siegel says, with palpable sadness, that people don’t stop to talk to him on his porch as much as they used to. Word has got around that he is “a Trump supporter, so fewer people schmooze with me.”

Mr. Siegel is the author of several books, including “The Future Once Happened Here: New York, D.C., L.A. and the Fate of America’s Big Cities” (1997) and “The Revolt Against the Masses: How Liberalism Has Undermined the Middle Class” (2014). Just out is “The Crisis of Liberalism,” a selection of his recent political essays, published by the small, independent Telos Press.

He started as a man of the left, and still describes himself as a protégé of Irving Howe, the democratic socialist literary critic. “Howe died young,” Mr. Siegel notes—in 1993, at 72. He was a doctoral candidate at the University of Pittsburgh in 1968, studying the political economy of tobacco in Virginia, when he cast his first vote. But he sat out the 1972 election. “I voted for Humphrey. I did not vote for McGovern or Nixon. I worked for McGovern as a spokesperson in Western Pennsylvania, and I was stunned to discover that he thought Henry Wallace had been right about a lot of things. Lightbulbs went off.”

In 1976 he voted for “Gerald Ford, the man.” Ford was “moderately competent and unpretentious. Jimmy Carter was pretentious. I thought his religiosity was painted on.” His aversion to Mr. Carter persisted, and in 1980 he backed John Anderson, a liberal Republican running as an independent.

Mr. Siegel voted for Walter Mondale over Ronald Reagan in 1984. “If anyone was going to make the Great Society work—and it was a mess by this time, a farrago—it was Mondale.” Mr. Mondale had “intelligence and knowledge,” but his defeat, and Reagan’s notable successes, made Mr. Siegel “rethink a lot of things.” A man like Mondale, he says, “would not be possible in today’s Democratic Party. There’d be no room for him.”

By the late 1980s Mr. Siegel had become “a centrist Democrat—part of a group that no longer exists.” Michael Dukakis was too liberal for Mr. Siegel, so he skipped the 1988 election. He became a fellow at the Progressive Policy Institute, the think tank of the centrist Democratic Leadership Council. He voted for Bill Clinton in 1992 and 1996 and advised—“but didn’t invoice”—Mrs. Clinton on her successful 2000 bid for Senate.

He didn’t vote in 2000 or 2004 and thinks George W. Bush “was a horrible president”: “The conduct of the Iraq war was extraordinarily inept. I supported the war initially, but I watched how it was being conducted, and I changed my mind.” The first time he voted for “the Republican Party as a party” was in 2008, by which time he had started to define himself as a conservative.

By 2012, when he voted for Mitt Romney, Mr. Siegel had developed an exceedingly low opinion of President Obama, whom he describes as “a faux intellectual with preacher’s cadences and an academic veneer.” In his opinion, “the worst thing” about Mr. Obama was “his effect on race relations. We couldn’t have the cold civil war we have now without Obama, because he, in a very cunning way, exacerbated all of our racial tensions.”

Under Mr. Obama, Mr. Siegel says, “racial grievance” took on a “new legitimacy, and it came from a president talking in asides, and saying things between the lines. He didn’t push back against anything, not even against the idea that Michael Brown said ‘Hands up, don’t shoot’ in Ferguson [Mo.], which was just a fabrication.”

Yet Mr. Siegel traces the origins of the “present-day contempt” for the middle class back a century. He cites H.L. Mencken’s demeaning of the bourgeoisie, in the celebrated editor’s coinage of “booboisie.” Mr. Siegel has written extensively on Herbert Croly, the political philosopher and co-founder of the New Republic, as well as on the novelists H.G. Wells and Sinclair Lewis (who, in 1930, became the first American to win the Nobel Prize for Literature). These three men, Mr. Siegel says, laid the foundation for an elite revolt against the American middle class that endures to this day.

“Croly’s idea was that the college-educated, the elite, should become a new aristocracy,” Mr. Siegel says. “Croly believed that the middle-class and their allies—latter-day Jeffersonians who advocated individual freedom and acted in their own self-interest—were impeding the path of the experts, who were ‘disinterested.’ ”

Wells and Lewis bolstered the view that the professional class was above the fray, giving the argument an almost aesthetic hue. “They thought the middle class was vulgar,” Mr. Siegel says. Mr. Siegel cites a passage in Lewis’s novel “Main Street” (1920), which he regards as “a sardonic sally at the small-town American middle class and its commercial culture.” In the passage, Carol Kennicott, a young woman from the big city trapped by marriage in small-town America, describes Americans as “a savorless people, gulping tasteless food, and sitting afterward, coatless and thoughtless, in rocking chairs . . . and viewing themselves as the greatest race in the world.” In a word, deplorables.

Croly has been largely forgotten, Mr. Siegel says, because liberalism has been largely eclipsed. “Wokeism is not liberalism,” he says. “I don’t want to be unfair to liberals. I was very critical of liberals, but they were in favor of debate; they were in favor of empiricism, of open argument.” Wokeism, by contrast, is a “new secular revealed religion,” which involves no “investigation or empirical study.”

The eclipse of the old “Crolyite liberalism” began, Mr. Siegel says, in the 1980s and ’90s, with the eruption of postmodernism into American intellectual life. “There began to be an emphasis on ‘narratives’ and feeling, which undermined the Crolyite emphasis on empiricism and evidence.” Liberalism had already been weakened by Reagan’s victory in 1980. “There was questioning among liberals, and some self-doubt,” Mr. Siegel says. “But the questioning didn’t go far enough, and blame was placed squarely on Carter. He didn’t check all of Croly’s boxes, he wasn’t a natural, Ivy League aristocrat. He was a farmer”—in contrast with John F. Kennedy, an archetypal Crolyite president.

There was, Mr. Siegel says, an ideological “hiatus” under Mr. Clinton, in which a party that had been “demoralized by the defeat of the technocrat Dukakis in 1988” recovered some of its mojo. But “postmodernism turning to wokeness was churning” in the 1990s. The 2000 election was “a trauma” for the Democrats, and Howard Dean’s unsuccessful candidacy for the 2004 nomination previewed “some of the craziness and hysteria that would come full-bore, on a broader scale, a decade later.” Wokeism achieved its apotheosis in 2014, in the aftermath of Michael Brown’s shooting. “Ferguson allowed Ivy League grads to assert their ‘natural leadership,’ in opposition to lowlife cops and guys with pickup trucks—again, the deplorables.”

In Mr. Siegel’s understanding, wokeism holds that “the important truths are already known, and that the American aristocracy has to impose those truths on the country.” These are “given positions”—irrefutable and sacrosanct. Wokeism, he says, is a “perilous threat” to America and particularly to the First Amendment. “It says we don’t need debate. We don’t need free speech. We don’t need freedom of religion. We need to obey.” Mr. Siegel’s vote is his personal act of disobedience.

Mr. Varadarajan is a Journal contributor and a fellow at New York University Law School’s Classical Liberal Institute.