In the days since British Prime Minister Theresa May’s disastrous snap election, the Labour Party and its leader, Jeremy Corbyn, have been taking in the sheer surprise of their upset near-victory: gaining 30 seats after being down some 20 points in the polls only weeks ago. While May’s Conservatives won the most seats in the election—an election the prime minister expected would give her a mandate to negotiate the U.K.’s exit from the EU—they fell short of an outright majority.

May is no doubt competent, but she campaigned so disastrously that her astronomical lead evaporated in less than two weeks. Like Hillary Clinton in America last November, she offered the same microwaved establishment gruel that nearly everyone on both ends of the spectrum has been gagging on for years. Corbyn, by contrast, was, like Donald Trump, the underdog populist from beyond the Westminster bubble, known for jousting with the political class in both parties.

If the election had been decided based on enthusiasm rather than votes, Corbyn would have cleaned up. The British left’s grievances with the centrist wing of the Labour party are nearly identical to progressive complaints about the Clinton wing of the Democratic party. Under Tony Blair and Gordon Brown, Labour distanced itself from those floundering at the bottom of the economy, fixating instead  on the upper-middle and managerial classes. Corbyn, a Labour MP for 34 years before becoming the leader of the party in 2015, embodied those grievances, promising in plain English to kick over the rubbish bins in London. He shares qualities with Bernie Sanders, who praised him last weekend during a three-day speaking tour in the U.K. Also like Sanders, Corbyn is a star among the young: More than two-thirds of voters younger than 25 told pollsters they wanted Corbyn to move into 10 Downing Street. The party’s stirring online manifesto, #WeDemand, has been shared more than 10,000 times on Facebook alone. Corbyn could have called it “Make Britain Fair Again” if it wouldn’t have all but plagiarized Donald Trump’s slogan. If he had been a little more mainstream, last Thursday would have been his.

But Corbyn, in some disturbing ways, is more like Trump than he and his supporters care to admit. The Western world, so far, seems incapable of nominating an anti-establishment populist without resurrecting ghoulish attitudes once considered extinct, like a zombified Tyrannosaurus Rex bubbling up out of the tar pits. Corbyn’s problems represent more than just the rough edges of a career back bencher suddenly thrust onto the dais—there’s an unrefined quality to his world view, a blinkered embrace of far-left positions over the years that make him seem divorced from reality. If left-wing populists don’t jettison their hoarier positions, they risk wreaking as much havoc as their right-wing populist counterparts—if they ever win outright, of course.

Corbyn isn’t an anodyne Danish-style socialist; at times, he seems willing to go all-in, Venezuela-style. He’s so far to the left that he makes Sanders look like Dick Cheney. “Thanks Hugo Chavez for showing that the poor matter and wealth can be shared,” he tweeted in 2013. “He made massive contributions to Venezuela & a very wide world.” Venezuela, for the record, is currently suffering chronic shortages of everything from food to toilet paper, a mass civil insurrection and murderous police brutality. Last November, Corbyn hailed Cuba’s dead communist dictator Fidel Castro as “a champion of social justice.”

There’s also Corbyn’s embrace of a virtual planet-wide rogue’s gallery of dictators and terrorists. “It will be my pleasure and my honor to host an event in parliament,” he said two years ago,“where our friends from Hezbollah will be speaking. ... I also invited friends from Hamas to speak as well.” Moments later, never-minding Palestinian suicide-bombings and rocket attacks against Jewish civilians, he insisted that Hamas is dedicated to “long term peace and social justice” and that Britain’s labeling of it as a terrorist organization is “a big, big historical mistake.” He reportedly praised Muammar Qaddafi’s “achievements” right at the moment NATO was debating whether or not to intervene on behalf of Libya’s civilian population in Benghazi, an intervention he opposed along with every other military action the U.K. has participated in since World War II. And while he has insisted that former prime minister and fellow Labour Party member Tony Blair should stand trial for war crimes, he was part of a movement in parliament opposing the U.K.’s decision to strike against Serbia’s Slobodan Milosevic—an actual genocidaire— denying that the butcher of Belgrade attempted yet another round of ethnic cleansing in Kosovo in 1999.

Corbyn also appeared on Iran’s hysterical state-run propaganda channel Press TV as a paid guest, even after the U.K. suspended its broadcasting license. When U.S. Navy SEALs killed Osama bin Laden, Corbyn went on the channel to complain that there was “no attempt whatsoever that I can see to arrest him and put him on trial, to go through that process” and that “this was an assassination attempt, and is yet another tragedy, upon a tragedy, upon a tragedy.”

Trump’s surreal chumminess with Russia and his refusal to reaffirm NATO’s mutual defense clause in Article 5 in his big speech in Brussels is straining the Western alliance, but Corbyn is almost as hostile to transatlanticism as French far-right populist Marine Le Pen, who wants to withdraw from NATO entirely. “NATO belligerence threatens us all,” he wrote in an article for The Morning Star in 2014, a newspaper founded by the Communist Party of Great Britain. He has said that NATO should have been dissolved in 1990, and that it should pull back from the Baltic border with Russia.

All this seems motivated, at least in part, by extreme pacifism and anti-imperialism rather than sympathy for dictators and terrorists, per se. Acknowledging that the likes of Milosevic, Qaddafi, Hezbollah, and so on, are as dangerous as their Western enemies claim bolsters the case for war against them, which Corbyn, as a leader of the U.K.’s Stop the War Coalition, cannot abide.

But none of that explains Corbyn’s enabling of anti-Semitism within his own party. In a report last fall, parliament’s Home Affairs Committee determined that the Labour Party under Corbyn has become a safe space for “those with vile attitudes towards” Jews. “The failure of the Labour Party,” the report said, “consistently and effectively to deal with anti-Semitic incidents in recent years risks lending force to allegations that elements of the Labour movement are institutionally anti-Semitic.”

Hate crimes against Jews, meanwhile, surged a staggering 60 percent in London last year and they’re up an additional 11 percent in the first six months of this year. Jewish members of parliament routinely receive death threats from self-described Corbyn supporters. One of them, Ruth Smeeth, a member of his own party, said she has saved more than 25,000 anti-Semitic emails from his partisans.

In a survey by the Jewish Chronicle from late May, 77 percent of British Jewish voters said they planned to vote for the Tories in the recent election. Britain’s Jews are not naturally conservative, but they view the Labour Party as dangerous.

Corbyn’s record on these matters does not acquit him well. He has defended a mural in London with anti-Semitic undertones, consorted with a Holocaust-denying outfit for more than ten years, and laid a wreath on the grave of a Palestinian terrorist directly involved with the murder of nine Israeli athletes at the Munich Olympics in 1972.

In their endorsement of Corbyn, the editors of The Guardian expressed their wish for “a different, fairer, better and more decent Britain—one that is less divided and more socially just; one that is more hopeful and less fearful.” And yet, they still saw fit to back Corbyn, despite his garish and (under normal conditions) disqualifying flaws because they prefer his policies to the other party’s.

The Western left is not immune to its own version of Trumpism, where a catastrophically bad candidate from one’s own party is preferable to a more or less mainstream candidate from the other. Normalizing extremism, paranoia, and hatred damages a society’s social and political fabric. In the end it’s also likely to render a party’s brand and reputation toxic for years to come.

British voters managed to contain the dangerous elements of the Labour party’s populism by keeping a Tory-led government in power for the foreseeable future. Next time around, Labour might want to clean its own house. Had the party’s voters chosen a leader—from either the socialist or the centrist wing—without Corbyn’s creepy extremism, it probably would have won in a landslide.