Almost all major Democratic candidates for president in 2020 will not attend next week's American Israel Public Affairs Committee (AIPAC) conference after the radical left group MoveOn.org called for a boycott of the event.

"The influx of progressive candidates confirming they will not attend — even those who have gone in years past — shows how the momentum is shifting," Iram Ali, campaign director at MoveOn, said in a statement Wednesday. "AIPAC is clearly a partisan lobbying group that has undermined diplomatic efforts, and progressives want no part in it." As of Thursday evening, aides for at least eight candidates told The Hill or other news outlets they would not attend this year's conference: Sens. Kamala Harris (D-Calif.), Bernie Sanders (I-Vt.), Kirsten Gillibrand (N.Y.) and Elizabeth Warren (D-Mass.); former Rep. Beto O'Rourke (D-Texas); South Bend, Ind., Mayor Pete Buttigieg; Washington Gov. Jay Inslee; and former Housing and Urban Development Secretary Julián Castro. An eighth candidate, former Rep. John Delaney (Md.), a centrist who is considered a long shot, is also not attending, but a spokesman said it was only due to a "scheduling conflict."

Former vice president Joe Biden, who spoke at the AIPAC conference in 2016, has not indicated whether he will attend or not.

AIPAC is not "clearly a partisan group," as it has welcomed speakers from both parties in the past. Indeed, the boycott seems to be over anti-Semitic remarks by Rep. Ilhan Omar — specifically, the rancid charge of "dual loyalties" by AIPAC members and other U.S. supporters of Israel. There was considerable criticism of Omar's nauseating anti-Semitism, including from several prominent Democrats.

But the boycott by Democratic presidential candidates shows an extremely worrying fact: the radical anti-Semites on the left fringe of the Democratic Party are gaining power and influence. There is already talk of pushing a "Boycott, Divest, Sanction" plank in the 2020 party platform, and how much do you want to bet that Rep. Omar and her fellow travelers will be featured speakers at the event?

AIPAC will be fine without the support of the anti-Semites, who have apparently terrified the 2020 Democratic field into not showing up. In the past, Democratic ambivalence on Israel has not led to much of a decrease in the Jewish vote. Jews are among the party's more reliable allies. But this is different, and thoughtful Democrats like Senator Chuck Schumer know it. Whether the shrinking pro-Israel faction in the Democratic Party can reassert its influence remains to be seen.