It isn’t just Israel and its relationship with the United States that bothers Buchanan; the man clearly has a problem with Jews. In his vigorous defense of accused Nazi war criminal John Demjanjuk (a dubious case for anyone, never mind a man with a reputation for Jew-baiting, to take up), he bordered on Holocaust denial, alleging in 1990 that diesel engines, whose exhaust was used to murder people in the Treblinka gas chambers, “do not emit enough carbon monoxide to kill anybody.” A full “half of the 20,000 survivor testimonies in Yad Vashem memorial in Jerusalem,” he wrote in 1990, “are considered ‘unreliable,’ not to be used in trials.”

While it was Buchanan’s latest book that did in his career as an MSNBC talking head, his 2008 tome, Churchill, Hitler and the Unnecessary War, was even more disturbing. As the title implies, Buchanan believes that the war to defeat Nazism was not only “unnecessary,” but also provoked by the Allies—not the racism and bloodlust of Adolf Hitler. As for the extermination of European Jewry, it was “not a cause of the war but an awful consequence of the war”—in other words, the Allies’ fault.

This is more than just shoddy history; it is the intellectual capstone to a career devoted to portraying Jews as a perfidious force in history. And in light of his views on World War II, Buchanan’s latter-day opposition to the wars in Iraq and Afghanistan, and American intervention abroad more generally—and his placing the blame for these wars on shadowy “neocons” or Israel’s “amen corner”—seems less principled. Yet none of this seemed to bother MSNBC or its fans. The man deemed anti-Semitic by the founder of the American conservative movement in 1992 was considered kosher by MSNBC ten years later.

Presumably, if enough of the station’s viewers had a problem with Buchanan, they would have voiced their concerns long ago and the network would have done something about it. But Buchanan’s decade-long presence on MSNBC served two paradoxical purposes for the network’s liberal viewers. Buchanan was the perfect foil for a cable news outlet devoted to characterizing the American right as old, white, and out of touch. He reassured liberals of their own cosmopolitanism and tolerance.

Yet, as the Bush administration wore on and the wars in Iraq and Afghanistan became increasingly unpopular, Buchanan’s foreign policy worldviews were echoed by the left. The war that most Democrats had supported was now a “lie” foisted on the country by duplicitous “neocons.” The recent controversy over the term “Israel-firster,” a noxious attempt to impute dual loyalties to American Jews, used by employees of the Center for American Progress and Media Matters, is the culmination of right-wing rhetoric finding a home on the mainstream left.

Excoriating those who agitated for his termination from MSNBC, Buchanan couldn’t help but dog-whistle to his anti-Semitic fan-base. “They operate behind closed doors, with phone calls, mailed threats, and off-the-record meetings,” Buchanan wrote, in a sentence that could have been ripped from the pages of the Protocols of the Elders of Zion. “They work in the dark because, as Al Smith said, nothing un-American can live in the sunlight.” Of course, the drive to end Buchanan’s career at MSNBC was anything but secretive: An Internet campaign designed to encourage viewers to flood network executives with e-mails and phone calls isn’t the stuff of cloak and dagger. That such an effort was required to persuade a network with the slogan “lean forward” to yank back its microphone from America’s most prominent reactionary, however, is a distressing commentary about the state of the contemporary left.

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James Kirchick is a contributing editor for The New Republic and a fellow with the Foundation for Defense of Democracies.