A few weeks ago, the sensationalist politician Michele Bachmann did her best imitation of the late Senator Joseph McCarthy. She and four of her colleagues in Congress released letters they had sent to the departments of State, Justice, Defence and Homeland Security, calling on them to investigate whether "operations conducted by individuals and organisations associated with the Muslim Brotherhood ... had an impact on the federal government's national security policies".
Warning of "determined efforts by the Muslim Brotherhood to penetrate and subvert the American government as part of its 'civilisational jihad'", the representatives wanted the government to identify Muslims who were influencing US policy.
In making these charges, Ms Bachmann and her colleagues were relying on the work of a Washington-based group, the Center for Security Policy, a notorious player that has been working for several years to smear Muslim American groups. The only source cited in the letters was the Center's "training programme": The Muslim Brotherhood in America: The Enemy Within.
The "evidence" is, at best, slight. For example, Representative Louie Gohmert says "this [Obama] administration continues to bow down before groups associated with the goal of destroying western civilisation from within" - by which he meant Washington's apology to Muslims after the Quran-burning incident in Afghanistan.
Ms Bachmann also points accusingly to some Muslims who serve in the administration, including Huma Abedin, Secretary of State Hillary Clinton's deputy chief of staff.
In Ms Abedin's case, the game goes from the absurd to the downright bizarre. Her parents are Muslims and her father taught at a university in Saudi Arabia, and so they must be ... fill in the blank.
In a Washington Times article inspired by the Center's work, questions were asked as to whether Ms Abedin "had been groomed to access movers and shakers to advance the cause of Islam in America". The article goes on to question whether Ms Abedin's marriage to a Jewish former member of Congress was a clever ruse designed to further this "Islamist agenda".
The evidence? Since Ms Abedin is a Muslim, why else would her family have approved of her marrying a non-Muslim? And, after all, she works for Ms Clinton, who shares the "socialist agenda, which includes domination of the US by a Muslim-ruled world".
What is so intriguing about these conspiracy-minded loonies is how the gravity of the threat grows each time they speak. In a recent interview, Ms Bachmann explained: "It appears that there has been deep penetration in the halls of our United States government by the Muslim Brotherhood."
As outrageous as this behaviour is, the charges have generated very little media attention, but that doesn't mean that they can be dismissed for two reasons: although all a bit looney, these politicians hold positions of influence on key Congressional committees; and witch hunts, if left unchecked, can ruin lives and damage reputations.
As was the case during the McCarthy era, equally troubling is the distress that campaigns of this sort can bring to those not named, but who live in fear that their religion or their ethnicity will be the reason that they will be held in suspicion. As I know from bitter personal experience, entire communities can be shunned by officials who fear being attacked for associating with a "dangerous" group. Because there is a scarcity of courageous leaders in Washington, all too often such witch hunts will persist.
It is for this reason that I am so thankful that the voters of Minnesota have sent Keith Ellison to Congress. He is smart, picking his fights carefully. Mr Ellison demonstrated his leadership this week when he directly challenged Ms Bachmann.
In a stern letter to Ms Bachmann and company, Mr Ellison asks that she provide "a full accounting of the sources you used to make the serious allegations ... If there is not credible, substantial evidence for your allegations, I sincerely hope you will publicly clear their names".
James Zogby is the president of the Arab American Institute
On Twitter: @aaiusa