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Jeremy Corbyn, the leader of Britain’s Labour Party, has a long history of playing footsie with bigotry — specifically with anti-Semitism.

“Over the years, he has attended protests and conferences alongside campaigners who have expressed anti-Semitic views,” Sam Knight, the London-based New Yorker writer, has noted. As Josh Glancy of The Sunday Times of London detailed: “Mr. Corbyn has described the constitutionally genocidal Hamas as his ‘friends.’ He’s appeared on stage with inveterate anti-Semites. He’s defended a mural that depicted hooknosed bankers running the world. He’s attended a wreath-laying ceremony that celebrated the perpetrators of the Munich Olympics massacre.”

When confronted about these instances, he has repeatedly claimed to have been unaware of his friends’ hatred. “Corbyn has an odd knack for stumbling into the arms of the Hebraically disinclined,” my colleague Bret Stephens has written.

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Is Corbyn himself a bigot? I have no idea. I assume he is not. But political leaders bear a responsibility for their public allies. Andrew Gillum, the Democratic nominee for governor in Florida last year, offered the pithiest version of this case, when describing his opponent, now-Governor Ron DeSantis: “I’m not calling Mr. DeSantis a racist. I’m simply saying the racists believe he’s a racist.”

In Corbyn’s case, anti-Semites are clearly comfortable working with him. He has been slow to apologize for cozying up to them and has done so only after intense criticism. His approach has had some similaritiesto the wink-wink relationship that some Republican politicians in the United States have with white nationalists.

On Sunday, Corbyn and Alexandria Ocasio-Cortez, the new star of the left flank of the Democratic Party, spoke to each other by phone about building a new trans-Atlantic political alliance. “Great to speak to @AOC on the phone this evening and hear first hand how she’s challenging the status quo,”he tweeted. She responded, “It was an honor to share such a lovely and wide-reaching conversation with you, @jeremycorbyn!”

Most of the criticism of Ocasio-Cortez over the past few months has been somewhere between silly and unfair. She’s one of the most successful new Congress members in memory, pushing her populist, pro-climate proposals to the center of the national conversation. But her embrace of Corbyn is a mistake.