As the Great Depression dragged toward the end of its first decade in 1938, Father Charles Coughlin released the latest issue of his newspaper Social Justice. It reprinted that most notorious and persistent of anti-Semitic tracts, The Protocols of the Learned Elders of Zion. Coughlin's decision to disseminate the spurious conspiracy tale to his millions of followers was not just the same old Jew-hatred, even if part of his financing came from Henry Ford. It marked Coughlin's transformation from an ardent New Dealer, who had coined the phrase "Roosevelt or Ruin," to a divisive demagogue. The through-line from Coughlin the social democrat to Coughlin the biased provocateur was populism. The same ideology that had led him earlier in his public career to attack corporate power and unmediated capitalism, to champion labor unions and activist government, also enabled him to search for a scapegoat. Jews doubly sufficed, being portrayed by Coughlin both as interlopers in a Christian nation and as the stealthy "money changers" and "international bankers" prolonging the Depression for their own profit. The genuine anxiety and despair of American workers gave Coughlin his opening to present - eureka! - the alien enemy. I STARTED thinking about Coughlin and his grim evolution as I followed the last two presidential debates, one each for the Republican and Democratic candidates. As a Jew in particular, with a certain inherited seismograph for such things, I sensed the tremors of a modern-day version of expedient, insinuating blame, this time for immigrants, Hispanic immigrants especially. The current election season in America should have provided cause for genuine self-congratulation about our national tolerance. The two leading Democrats are, of course, a woman (Hillary Clinton) and a mixed-race half-African partly raised in the Muslim world (Barack Obama). The fact that Clinton and Obama are battling so intensely for African-American votes shows that the era is over when whites would rarely vote for a black and blacks would rarely vote against one, irrespective of merits. Meanwhile, on the Republican side, the Christian Right's veto power over any nominee has seemingly been broken. Rudolph Giuliani has led in many polls despite his longtime support for abortion rights and his shall-we-say checkered record of personal morality. Even Pat Robertson endorsed him. Whether or not Giuliani wins the nomination, he has shattered the conventional wisdom about abortion and "family values" being the litmus tests for any GOP contender. All these causes for relief, and even optimism, however, have been outweighed by the surging role of nativism in the campaign. Virtually every major candidate except John McCain has backed away from his or her own admirable position on immigration - Huckabee's program of merit scholarships for undocumented immigrant students while he was governor of Arkansas; Giuliani's principled refusal as mayor of New York to poke into residents' immigration status. The Democrats fall over each other insisting on th e necessity of English as the national language while the Republicans scramble to outdo each other with plans to seal the Mexican border. None of these candidates exactly fill the Coughlin role - that part belongs to the pseudo-journalist Lou Dobbs - but all have plainly decided to appeal to the worst angels in the American national character. With middle-class income stalled for years, with a major recession looming thanks to the subprime mortgage scandal and the Bush administration's reckless spending, somebody has to be blamed, and that somebody is the illegal immigrant, invariably Hispanic. Campaign 2008 is a race to the bottom, morally speaking. Yet the campaign also keeps reminding us that illegal immigrants are the elephant in the room, the presence nobody wants to acknowledge. Mitt Romney has recently had to concede that illegal immigrants did some of the landscaping outside his Massachusetts mansion. Mike Huckabee's progressive record on immigration as governor of Arkansas reflected the economic and demographic reality that Hispanic immigrants, with or without papers, are filling the state's many jobs in the poultry industry. Only a candidate with no prospect of winning dares to speak logically. In the Democrats' debate in Iowa last week, Joseph Biden pointed out that in every wave of immigrants coming to the United States the generation of American-born children has become fully fluent in English. The even more quixotic Dennis Kucinich noted that the founding documents of Ohio, his home state, were written in German. The process of assimilation happens for practical reasons - going to school, looking for a job, asking directions. It happens through the pervasive influence of popular culture, as any immigrant who learned the language by having the TV or radio on all day can attest. EVIDENTLY, the leading candidates (again, with McCain as the valorous exception) believe there is no downside to bashing illegal immigrants, since by definition they do not vote. I think they misread the way the millions of immigrants who have become citizens in the past decade or two hear their calumnies. These fully legal Americans encounter suspicion and bigotry that has been set loose, indeed made socially permissible, by the attacks on illegal immigrants. The headway that Ronald Reagan made with socially conservative immigrants, both Hispanic and Asian, was squandered in 1992, when the Republican Party was suffused with Patrick Buchanan's rhetoric of culture war. George W. Bush's popularity with Hispanic voters began to erode in the 2006 midterm elections. This year, however, the leading Democrats have felt the need to prove their nationalist credentials by criticizing free trade and globalization, which is just another way of saying that our problems are due to outsiders and open borders. It will be an exercise in contortion to watch Clinton, Obama or John Edwards, whoever winds up the nominee, straining to appeal to immigrant voters in the general election while still pandering to the people who think Mitt Romney's landscaper is the cause of everything that ails the body politic. The writer is a professor of journalism at Columbia University.