WASHINGTON — Days after announcing his opposition to the Iranian nuclear deal, Democratic Senator Chuck Schumer has faced an onslaught of allegations from progressive critics who resorted to classically anti-Semitic allegations of disloyalty and treason. The Anti-Defamation League criticized the accusations Monday, telling The Times of Israel that such accusations are a “slap in the face” to Schumer’s long years of service to the United States.

Schumer announced last Thursday that he would oppose the nuclear deal with Iran when it faces a crucial vote in Congress next month. His defection from the Obama administration’s side on the issue was a blow to White House efforts to prevent the two-thirds majority in Congress against the deal that might overcome a presidential veto — but was hardly unexpected from a legislator who had already indicated his discomfort with the agreement.

Since Schumer’s announcement, a Twitter hashtag #dumpschumer has become the focal point for much of the vitriol. Nominally devoted to a drive to prevent Schumer from taking the reins of Senate Democratic leadership after Minority Leader Harry Reid leaves the position, anti-Schumer campaigners refer to him repeatedly as a “traitor,” suggest that his loyalty lies only with Israel and not the United States, and accuse him of receiving his “real paycheck” from nefarious sources — which they characterize as Israel, the American Israel Public Affairs Committee (AIPAC) or other pro-Israel bodies.

But the notoriously provocative twitterverse is not the only outlet for such accusations.

The progressive website Daily Kos ran a cartoon in which an imaginary television host called a woodchuck version of Schumer a “traitor” and switched the American flag at Schumer’s side to an Israeli flag.

“The reactions are a sad example of how some individuals buy into the kind of thesis promoted by [John] Mearsheimer and [Stephen] Walt that US Jews and other supporters of Israel put Israel’s interests ahead of US interests,” said Anti-Defamation League National Director Jonathan Greenblatt.

Walt and Mearsheimer co-authored a paper and later a 2008 book in which they claimed that the “Israel lobby,” a loosely defined cross-section of American Jewish groups and others, works against US interests. They said it was characterized by “a core consisting of organizations whose declared purpose is to encourage the US government and the American public to provide material aid to Israel and to support its government’s policies, as well as influential individuals for whom these goals are also a top priority.”

Critics complained that Mearsheimer and Walt essentially reinvigorated classical anti-Semitic tropes accusing Jews of acting as a “nation within a nation” and possessing dual and conflicting loyalties.

Walt, in fact, was one of those who tweeted and retweeted responses to the current back-and-forth over whether the rhetoric concerning the Iran deal constituted anti-Semitism. The Harvard professor called Schumer a “sellout” and retweeted an opinion article in the Huffington Post that called the deal’s opponents “Netanyahu’s marionettes.”

That article cited Schumer’s 2010 comments in which he reportedly said “I am a shomer [guardian] for Israel and I will continue to be that with every bone in my body” as evidence of his unpatriotic interests.

“Hurling accusations of disloyalty are a slap in the face to his [Schumer’s] lifelong record of public service,” Greenblatt complained in a written response to the rhetoric. “There is room for a legitimate debate on the Iran deal, however charges against Senator Schumer — and any other members who articulate on fact-based but alternative views — are beyond inappropriate.”

Proponents of the Iran deal — including President Barack Obama himself — have been criticized in recent weeks for what some see as criticism of their opponents that ply on historical stereotypes of Jews.

Over the weekend, the Jewish magazine Tablet’s editors penned an unusually strident editorial condemning what editors — including both supporters and opponents of the deal — describe as “the use of Jew-baiting and other blatant and retrograde forms of racial and ethnic prejudice as tools to sell a political deal, or to smear those who oppose it.”

The Tablet editors, writing two days after Schumer’s announcement, complained that “accusing Senator Schumer of loyalty to a foreign government is bigotry, pure and simple.”

Tablet described “this use of anti-Jewish incitement as a political tool” as a “sickening new development in American political discourse.”

The editors placed responsibility for its emergence at the highest levels of the administration, citing Obama’s own rhetoric including mentions of shadowy moneyed lobbyists, foreign interests, and warmongers as “a direct attempt to play the dual-loyalty card.”

“It’s the kind of dark, nasty stuff we might expect to hear at a white power rally, not from the President of the United States — and it’s gotten so blatant that even many of us who are generally sympathetic to the administration, and even this deal, have been shaken by it,” the editors wrote.

While the entire Republican caucus and a number of other Democratic legislators — including Reps. Eliot Engel and Grace Meng — have come out in opposition to the deal, Schumer has faced the strongest onslaught of criticism.

In his comments, the ADL’s Greenblatt highlighted the fact that Schumer “is entitled, like every legislator, to express what he feels is best for the United States and the region on the proposed deal.”

Schumer waited some three weeks after the text of the nuclear deal reached Congress before making his announcement. During that period, he faced intense pressure from anti-deal activists, who held demonstrations outside of his offices calling on him to come out in opposition to the deal.

Even after his announcement, the New York senator continues to be at the epicenter of the legislative fight over the deal. On Monday, the Zionist Organization of America called on supporters to continue to pressure Schumer to recruit other legislators to oppose the deal, while the progressive MoveOn.org urged its supporters to refuse to donate to Schumer or any Democrat who opposes the deal.

Schumer’s office, which was deluged with phone calls on Monday, did not respond to a request to comment.