Progressives are taking the initiative to destroy and defeat accusations that Sen. Bernie Sanders, a frontrunner for the 2020 Democratic presidential nomination, is running or at the least tolerating an anti-Semitic primary campaign—accusations that come while the right-wing sharpens its knives for the Vermont senator as he rises in the polls.

Attacks against Sanders began last week after U.K. Labour Party leader Jeremy Corbyn suffered a humiliating defeat that some observers believe was helped by years of attacks claiming he and his left-leaning British party were anti-Semitic. At that point, columnist Peter Beinart wrote for The Forward on Tuesday, the die was cast.

“Given Bernie Sanders’ endurance as a top-tier presidential contender, and his support for Palestinian rights, it was almost inevitable that conservatives would start labeling his campaign anti-Semitic,” wrote Beinart. “Last week’s election in Britain—and the alleged similarities between Sanders and Labour Party leader Jeremy Corbyn—provided the pretext.”

It happened quickly. On December 13, right-wing outlet The Washington Examiner reporter Tiana Lowe—whose recent praise for her Nazi-collaborating Chetnik grandfather was noted by a number of observers—wrote that the Sanders campaign “has an anti-Semitism problem.”

The smear provoked a sharp reaction from Sanders speechwriter David Sirota.

“As a Jewish person, my response to this is simple,” Sirota tweeted, “anyone accusing Bernie of anti-Semitism—and anyone publishing this shit—is a total asshole.”

Bernie is a Jewish person fighting Trump’s hate-filled ideology. His family was murdered in the Holocaust because they were Jewish. As a Jewish person, my response to this is simple: anyone accusing Bernie of antisemitism — and anyone publishing this shit — is a total asshole. pic.twitter.com/3Hq9nH3RIf — David Sirota (@davidsirota) December 14, 2019

Lowe’s piece was joined by articles in other right-wing publications, including conservative magazine Commentary‘s online editor Noah Rothman. Cartoonist and activist Eli Valley hit back at Rothman on social media, saying, “It’s happening—elated over the U.K., the minority of American Jews that has waged war on the progressive Jewish majority for generations is starting to pull the same shtick with the most inspiring Jewish politician of our time.”

“We need to shut this shit down early,” Valley added.

That sentiment was shared by journalist Kate Aronoff, who, in a call to action, urged supporters of the senator’s campaign to fight against the attacks.

“Let’s nip this shit in the bud, team,” tweeted Aronoff.

Let's nip this shit in the bud, team. My latest for @guardian on Zayde Bernie and the craven slugs calling his campaign anti-Semitic: https://t.co/wrQxHIHLeg — Kate Aronoff (@KateAronoff) December 18, 2019

Aronoff pushed back on the accusations against Sanders, a Jewish man who had members of his family murdered in the Holocaust, for The Guardian Wednesday. In her essay, Aronoff argues that smearing Sanders as an anti-Semite or tolerant of anti-Semitism is rooted in both the senator’s support for Palestinian rights and seeking shameless partisan advantage from his opponents on the right.

“Before they snowball into something worse, the right’s allegations of antisemitism against the left—and the first Jew within striking distance of the White House, at that—should be called out for what they are,” wrote Aronoff, “cynical politiking in service of politicians who will put more Jews in danger.”

David Klion, news editor of left-wing Jewish magazine Jewish Currents, which recently published a piece on fighting anti-Semitism authored by Sanders, told Common Dreams that attacks on Sanders are about more than just the senator’s campaign.

“Sanders represents a strain of American Jewish identity that is profoundly threatening to the mainstream Jewish establishment—one rooted in social justice and solidarity with all oppressed peoples, rather than in Zionism, religious conservatism, or corporate-friendly politics,” said Klion. “Discrediting him as a Jew is really about discrediting left-wing Jews in general.”

Sen. Ted Cruz (R-Texas) on Monday attempted to make the case that Sanders’ friendship and political allyship with Rep. Ilhan Omar (D-Minn.), a Muslim woman of color, was evidence of a connection between the senator and anti-Semitic elements in the Democratic Party—an accusation against Omar of anti-Jewish bias.

In a blistering retort to Cruz, Never Again Action’s Sophie Ellman-Golan both called on Senate Minority Leader Chuck Schumer (D-N.Y.) to condemn Cruz and put the attacks on Sanders in context.

“Bernie Sanders’ willingness to criticize Israel, his support for Palestinian rights—these are not anti-Semitic, and I’ll be dammed if we let right-wing Christian evangelicals and right-wing members of our own community redefine them as such,” said Ellman-Golan.

Left-wing activist Twitter account Jewish Worker agreed.

“They’re not attacking Bernie because of anti-Semitism,” said Jewish Worker. “They’re attacking Bernie because of anti-Palestinianism. Don’t let them confuse you.”