As this year’s J Street conference begins, I’ve obtained a speech from last year’s—from a conference panel called “Working with Christian Communities Towards a Room Two-State Solution.” The speaker in question is Serge Duss, Director of the New Century Evangelicals Project, and the theory at issue is that modern Jews are not descended from Biblical Jews:

The misconception that most Evangelicals have, particularly conservative Evangelicals – I consider myself a progressive Evangelical – is what we learned in Sunday school. And what we learned in Sunday school about the Old Testament and particularly King David, we have carried forward three, four, five thousands years, where there is a belief that the modern state of Israel and modern Israelis are the extension of the Children of Israel of the Old Testament. You, only you – I can’t, but only you can disabuse Evangelicals of that mythology. How many rabbis I’ve heard say in settings, ‘We are not the Hebrews, the Children of Israel of the Old Testament’? And unless conservative Evangelicals particularly hear that message from Jews in America today and Israelis in Israel, minds will not be changed.

Under the most innocent reading Duss was merely calling for J Street’s Jewish attendees to use their Jewish identity to undermine support for Israel. That would be a telling advocacy, and here it’s worth noting that J Street organizers appreciated Duss so much that they brought him back this year. Instead of trying to expand the pro- Israel tent to include more people, J Street seems committed to isolating Israel and Israelis by undermining existing their support from American Jews and Christians.

But there’s very little innocent here. Denying the connection between ancient and modern Jews is, according to conspiracy theory expert Bob Blaskiewicz, “a precursor to the type of rationalization of Christian Identity theology, that the ‘Jews’ are imposters claiming the Chosen People status properly owned by the white American Christian male.” It’s a scientifically disproven canard that anti-Semites have used for centuries to disinherit Jews theologically and politically.

At its most explicit, the theory holds that contemporary Jews are descendents of non-Semitic Khazars who converted to Judaism. The Anti- Defamation League has an extended backgrounder on how the claim has played out in modern anti-Semitic movements. You can find it in the wild on Holocaust-denying WWII revisionist sites, in the forums of Protocols-obsessed David Icke, and on one of the Internet’s most notorious conspiracy theory cesspools. Note how quickly the writers transition from the theory itself into how it undermines the legitimacy of the Jewish State.

Duss’s notion that “modern Israelis are [not] the extension of the Children of Israel of the Old Testament” has entered the leftwing anti-Israel evangelical world via at least two routes. Among Christian Palestinians the Khazar theory has long been promoted by Mazin Qumsiyeh, who is heavily tied to the anti-Israel Arab Christian circuit. In the United States it was picked up by the Israel- Palestine Mission Network, a particularly nasty organ of the Presbyterian Church USA, and inserted into booklets based on a 2008 book by Israeli professor Shlomo Sand. From Sand it hopped elsewhere in the evangelical world, until by 2010 you had Palestinian Lutheran minister Mitri Raheb declaring at an evangelical conference that he’s descended from King David while Netanyahu has no Jewish blood and “comes from an East European tribe who converted to Judaism in the Middle Ages.”

Duss was a little ambiguous in his J Street speech, so no one knows whether he was specifically gesturing toward the Khazar theory and its political implications. It’s not impossible that Duss was just being metaphorical. Instead of intentionally using an anti-Semitic dog whistle to undermine American evangelical support for Israel, he would have been vaguely invoking a classically anti-Semitic trope to undermine American evangelical support of Israel.

Either way, by the standard J Street president Jeremy Ben-Ami set when he condemned the imagery in Netanyahu’s AIPAC speech, even metaphorical anti-Semitism would still leave J Street deeply complicit.