Less than four years ago, Jeremy Corbyn was an obscure backbencher in the British Parliament. In his 30 years as a member of the Labour Party, his greatest legislative accomplishment was paradoxically the lack of any: From 1997 to 2010, when Labour was last in government, Corbyn was the MP who voted against his own party more than any other. Despite his perpetual insubordinations, successive Labour Prime Ministers Tony Blair and Gordon Brown declined to expel Corbyn from their party. “There was no threat,” a deputy Labour chief whip told the Financial Times about Corbyn and his small band of hard-left rebels in 2016. “These people were tolerated because no one had ever heard of them.”Today, everyone in British politics has heard of Jeremy Corbyn, who, as leader of Her Majesty’s Most Loyal Opposition, has utterly transformed the Labour Party. Once a broad-based movement that could command large parliamentary majorities, today it is a sectarian personality cult, offering meager resistance to a shambolic Conservative government. Once the party whose leaders created NATO and stood stalwart against the threat of international communism, today Labour is led by people who sing the praises of anti-Western despots and terrorists. And once the natural political home of British Jewry, Labour today is mired in an anti-Semitic morass, to the point where 40 percent of Jews say they would “seriously consider” leaving the country were Corbyn to become prime minister. Indeed, Labour has become so toxic that, last month, nine MPs quit the party, calling it “sickeningly, institutionally racist,” “a threat to national security” and “a danger to the cohesion of our society, the safety of our citizens, and the health of our democracy.”How Labour reached this deplorable condition is one that should seriously concern liberals in the United States, where a similar dynamic is playing out in the Democratic Party. An insurgent progressivism favorably disposed to socialism, hostile to Jews and openly admiring of Jeremy Corbyn and all that he represents is steadily making inroads against an aging, centrist Democratic establishment. Here, a constellation of elected officials, media personalities, and activists are mimicking the tactics of their ideological comrades in Britain to take over and transform the Democratic Party into a vehicle for their extreme agenda.The devotees of American Corbynism congregate around Vermont Sen. Bernie Sanders, the “democratic socialist” who, like the British Labour leader, has a long record of overlooking the depredations of left-wing authoritarians abroad. A recently discovered video from 1988 shows the future presidential candidate regaling an American audience with the highlights of a recent trip he and his wife Jane made to the Soviet Union, where he rode on the “very, very effective” transportation system and was wowed by train station “chandeliers that were beautiful.” Just a year before the collapse of the Berlin Wall, these two political pilgrims sounded like Beatrice and Sidney Webb, British socialists who ventured to Josef Stalin’s Russia only to report back smiling peasants and abundant harvests. Sanders, who initially had positive things to say about the late Hugo Chavez’s Bolivarian revolution, today stubbornly refuses to call his successor, the brutal Nicolas Maduro, a dictator.It is in their defensive reactions to the ongoing turmoil in Venezuela that the American Corbynistas reveal their true colors. Congressman Ro Khanna, national co-chair of Sanders’ campaign, repeats Venezuelan government talking points about U.S. sanctions, claiming that they “hurt poor people the most.” (In reality, the sanctions target officials of the Maduro regime, which is preventing U.S. food aid from reaching the poor Venezuelans whom Khanna professes to care so much about.) Freshman Representative Ilhan Omar has repeatedly referred to a U.S. “coup” and retweeted a Venezuelan state propaganda mouthpiece. Her colleague Alexandria Ocasio-Cortez, the most popular of the American Corbynistas, refuses to condemn Maduro, preferring instead to trot out tired, Cold War-era talking points about the Trump administration’s envoy for Venezuela, Elliott Abrams. (Last month, Ocasio-Cortez engaged in a friendly phone chat with Corbyn, about which she enthused on Twitter.)American Corbynism also takes after its British provenance with hostility toward Jews. Over the past few weeks, Rep. Omar has made a succession of crude anti-Semitic statements, intimating that U.S. support for Israel is due to the influence of Jewish money and that American Jews are guilty of “allegiance to a foreign country.” Rather than denounce these statements outright, House Democratic leaders buckled under pressure from their progressive and black caucuses, which insisted that a resolution singling out anti-Semitism for denunciation be watered down to include reprimands against every other conceivable hatred. Leading Democratic presidential candidates have defended Omar, and some, like Sanders, went so far as to imply that it was somehow the representative from the Fifth District of Minnesota who was the victim in this brouhaha.The attempt to weaken a resolution condemning a specific case of anti-Semitism by lumping it in with other types of bigotry smacks of the mantra, cynically repeated by Corbyn and his followers whenever they are confronted with the bounteous examples of anti-Semitism from within their ranks, that they oppose “all forms of racism.” It also evokes the nauseating attempt by Corbyn and his shadow chancellor, John McDonnell, to rename Holocaust Memorial Day “Genocide Memorial Day,” an initiative they undertook because “every life is of value.” Last year, Corbyn and his supporters embroiled Labour in a protracted controversy over whether or not to accept the International Holocaust Remembrance Alliance definition of anti-Semitism, insisting that comparing Israel to Nazi Germany be exempt. This attempt to dilute the meaning of anti-Semitism is now being imitated by progressives who, like Sen. Elizabeth Warren, dishonestly say that Omar was just innocently offering “criticism of Israel” when she alleged that her congressional colleagues had been bought off by duplicitous, moneyed Jews. “Viewing American progressive politics today is like seeing the beginnings of a slow-motion car crash, one we’ve already been through,” observes erstwhile Corbyn supporter Rachel Shabi.A critical element of the trans-Atlantic Corbynista project is to knock Jews down a few pegs in the progressive victim hierarchy. Democratic House Majority Whip Jim Clyburn’s perverse defense of Omar–that her experience as a refugee is “more personal” than that of the children of Holocaust survivors, and that this somehow legitimates her spreading anti-Semitic conspiracy theories–was a clumsy effort at privileging Muslims over Jews. Omar and her defenders seek, in the words of New York Times columnist Ross Douthat, “a left-of-center politics that remembers the Holocaust as one great historical tragedy among many.” To achieve this reordering, Corbynism exploits fringe Jewish activists and organizations to deflect charges of anti-Semitism. As the most high-profile Jewish politician in America, Sanders has disgracefully assumed this role, alleging that Omar is being slandered for “legitimate criticism” of Israel, when it is her imputation of dual loyalties that is at issue. In so doing, Sanders lends credence to the view, increasingly prevalent among progressives on both sides of the Atlantic, that left-wing anti-Semitism does not really exist and that accusations of it are really just cynical attempts to forestall socialism and smear people of color. No other form of bigotry–whether anti-black racism, homophobia, misogyny, ableism–is subject to such exacting standards of proof and semiotic scrutiny by left wingers.Obsession with Israel—the decision to make this tiny country, and America’s relationship with it, the battlefield upon which they will try to wrest control of the Democratic Party away from its establishment leadership—is a window into the worldview of the American Corbynista left. Antagonism toward the only liberal democracy in the Middle East is like an acid test for wanting to reduce American global power and influence. Asked to describe Sanders’ worldview, his chief foreign policy advisor Matt Duss, a career anti-Israel polemicist, says that the United States should be “a kind of global facilitator.” Arsenal of democracy and leader of the free world are just so passé.For these people, condemning the U.S.-Israel alliance is a way of condemning something much larger than a country 10,000 miles away. Attacking the Jewish state is the means by which they express their broader antipathy toward American exceptionalism. America and Israel are exceptional nations, the only two founded upon an idea. They are linked by shared values and, yes, religious affinity. When Americans look at the Middle East, they naturally see Israel as the polity with which they have the most in common. American support for Israel, then, is not explained by “Benjamins,” as Ilhan Omar conspiratorially tweets, but by a deep and widely held conviction that the two nations share a providential fate. This is something which the American Corbynistas, like their British cousins, deeply resent, and thus try to undermine with their sneers and tweets and purges.Another feature that American Corbynism shares with its British counterpart is an intellectual network. Corbyn’s rise in British politics has been accompanied by the development of a left-wing media ecosystem which treats the Labour leader as Dear Leader, and is as impervious to reality as any alt-right news site. The most popular of these new outlets, Novara, refers to the developments in Venezuela as a “coup” and blames “sanctions and oil prices”—not socialist mismanagement and corruption—for the country’s devastation. In the United States, the increasingly influential Jacobin magazine declares that, “Only a deepening of the Bolivarian Revolution can save it” and, in a piece entitled “What You Need to Know about Venezuela,” refers to “so-called human rights abuses” perpetrated by the Maduro regime. In a sign of the developing links between the British and American variants of Corbynism, the owners of Jacobin recently purchased Tribune, a legendary left-wing magazine for which George Orwell was literary editor. (And, being good socialists, they fired and replaced the staff.)Chapo Trap House, a socialist, Sanders and Corbyn-supporting podcast broadcasting out of Brooklyn, (recently crowned the spiritual headquarters of the new socialism by New York magazine), collects over $100,000 per month in donations from some 25,000 subscribers, and has been the subject of fawning coverage in The New Yorker. “Who cares?” if the Soviets won the Cold War, the hosts ask in their recent book, The Chapo Guide to Revolution. That twilight struggle was “not about democracy versus totalitarianism” but “about capitalism versus threat to capitalism.” (Chapo, and its self-proclaimed legion of “dirtbag” leftists, offer yet another parallel between Corbyn and Sanders, who, like all political extremists convinced of their superior virtue, share a preternatural ability to attract the most vicious, vulgar, and juvenile supporters.)The final element that American Corbynism needs to succeed like its British counterpart is an organizational apparatus. Corbyn was able to take over the Labour Party through the practice of “entryism,” whereby his hard-left followers, (many of them members of various communist and Trotskyite groupuscules), joined Labour in droves and voted him into power after the party reduced its membership fee to just £3 and eliminated an electoral college system tilted toward the votes of MPs and union leaders. Momentum, the campaigning group which formed to support Corbyn’s leadership bid, continues to exist as a party-within-a-party, and is assiduously working to “de-select” Labour MPs who have dared criticize his leadership.Sanders’ association with the Democrats is even more tenuous than that of Corbyn’s to Labour. A lifelong independent who laments “the futility of liberalism,” he opportunistically joins the Democratic Party when it suits him, namely, when he decides to run for president. Like the hundreds of thousands of hard-left activists who joined Labour expressly to put its most radical and mutinous MP in charge, the rising cohort of American progressives are ideological interlopers and infiltrators, whose values, policies and tactics are at odds with those long espoused by the mainstream of the Democratic Party. The American Corbynistas have their own organizational and tactical analogues to Momentum and deselection in the Justice Democrats and Democratic Socialists of America (DSA), both of which are trying to pull the party far to the left by supporting primary challengers to Democratic incumbents deemed insufficiently progressive. Ocasio-Cortez, who, less than two months into her new job has already threatened to put some of her House Democratic colleagues on “a list” for progressive challengers to target, is one of two congressional members of the DSA, the other being Michigan Democrat Rashida Tlaib.American Corbynistas are the vanguard of the Democratic Party. Whether or not they take the leadership reigns in the next five years or 15, they’ve already pushed the party far to the left. The Green New Deal, Medicare for All, Modern Monetary Theory, tuition-free college—Democratic presidential candidates are constantly trying to out-left one another, as are leading progressive writers at major publications and the policy wonks jockeying for positions in a future Democratic administration. “Until very recently, it wasn’t that socialism was toxic in a red-scare way. It was irrelevant, in a dustbin-of-history way,” writes Simon van Zuylen-Wood in a cover story for the current issue of New York about the rise of Millennial socialism. “But then came Bernie Sanders’s 2016 candidacy, then the membership boom of DSA, then the proliferation of socialist cultural products like Chapo, and then, finally, the spectacular rise of Ocasio-Cortez.”To be sure, there exist some institutional hurdles in the United States complicating a full-scale Corbynization of the Democratic Party. Power in American politics is more widely dispersed, both geographically and structurally within the parties themselves, than in Britain, where a party leader in a parliamentary system can more easily impose top-down control. Jews have a more significant presence in the Democratic Party than in Labour. Most of the Democratic freshmen elected to Congress last November are moderates, who likely resent the way in which a handful of their colleagues are defining the party as radical in the eyes of many Americans. And as an idea, socialism has never held the same purchase in America as it does in Britain, where the National Health Service is almost as strong a symbol of national identity as the queen.Yet watching the emerging Democratic crackup, these reassurances sound eerily familiar. After all, it was only a few years ago that anxious conservative intellectuals and Republican elected officials were confidently pronouncing that there was no way a thrice-married reality television show star—who publicly doubted that the first black president was born in America, regularly spewed xenophobic invective, and spoke warmly of a Russian autocrat—could seize the presidential nomination of the GOP, never mind the presidency itself. A large reason Donald Trump was able to do all this is that, when it mattered, Republican elites repeatedly failed to draw the sorts of red lines that would have challenged him. As Britain is learning the hard way these days, a party that doesn’t erect guardrails to protect itself from extremists will eventually be captured by one.***Like this article? Sign up for our Daily Digest to get Tablet magazine’s new content in your inbox each morning.