Chuck Schumer is a politician—a skilled and successful one. Which means that today’s announcement, following months of wildly uncharacteristic silence, that the senior senator from New York is opposing the administration’s nuclear deal with Iran is first and foremost a reflection of his calculations as to where his own self-interest lies. It does not take an electoral genius to imagine why a senator from New York State might oppose a deal that keeps many Jewish voters—and an even higher percentage of non-Jewish voters—up at night. Keeping your base happy is generally the first rule of political survival.It also seems unlikely that Sen. Schumer would not have consulted with his most powerful political ally and patron, Hillary Clinton, who also happens to be the presumptive Democratic presidential nominee, before making such a big decision. Deciding to oppose a potentially world-altering legacy-oriented foreign-policy move by a sitting Democratic president is not the kind of thing that Democratic senators do lightly—especially with a presidential campaign now officially in progress. While Schumer doesn’t speak for Clinton or for her campaign, his decision to oppose the deal after months of pressure from the White House is a strong indication that neither Democrat felt like Schumer’s position was likely to have a particularly negative effect on her chances.So, what about the Iran deal itself? Some of us support the deal, because—like a majority of American Jews—we support the president, and we sympathize with his aims of ending Iran’s pursuit of nuclear weapons while keeping America out of another Middle Eastern war. Some of us oppose the deal because we believe that it falls very short of the criteria for meaningful limits on and inspections of Iran’s nuclear research programs that the administration itself repeatedly promised to America and the world. Some of us are less concerned with the specifics of the deal than with the prospect of an American alliance with the theocratic Iranian regime, which the deal appears to be designed to cement.As heated as the arguments between us can get, we can all agree that all of these positions, and their many variants, are entirely within the bounds of legitimate political debate—and that none of them are evidence of anyone’s intent either to rush America to war or to obliterate the State of Israel.What we increasingly can’t stomach—and feel obliged to speak out about right now—is 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. Accusing Sen. Schumer of loyalty to a foreign government is bigotry, pure and simple. Accusing senators and congressmen whose misgivings about the Iran deal are shared by a majority of the U.S. electorate of being agents of a foreign power, or of selling their votes to shadowy lobbyists, or of acting contrary to the best interests of the United States is the kind of naked appeal to bigotry and prejudice that would be familiar in the politics of the pre-Civil Rights Era South.This use of anti-Jewish incitement as a political tool is a sickening new development in American political discourse, and we have heard too much of it lately—some coming, ominously, from our own White House and its representatives. Let’s not mince words: Murmuring about “money” and “lobbying” and “foreign interests” who seek to drag America into war is 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.We do not accept the idea that Sen. Schumer or anyone else is a fair target for racist incitement, any more than we accept the idea that the basic norms of political discourse in this country do not apply to Jews. Whatever one feels about the merits of the Iran deal, sales techniques that call into question the patriotism of American Jews are examples of bigotry—no matter who does it. On this question, we should all stand in defense of Sen. Schumer.