The Republican presidential election campaign has not been especially blessed with sober discussion about foreign policy.

As WorldViews catalogued over the past few months, the GOP debates have had their fair share of bigoted and brutal rhetoric about the Middle East, and featured myriad incoherent and fantastical policy solutions to crises near and far.

After the narrowing of the field of candidates, you'd perhaps expect a bit more substance and heft to shape the conversation. Not so, at least judging by the most conspicuous name on the list of Sen. Ted Cruz's foreign policy advisers.

Bloomberg View reporter Eli Lake spotlighted the presence on Cruz's team of Frank Gaffney, a man whose views were "considered radioactive by the Republican establishment" until the race for the nomination began.

Gaffney, a former Reagan administration official, has operated from the political fringes over the past decade and is a prominent figure in the Islamophobic far-right. But his talking points proliferate among a wing of the GOP and gained traction in an election year where the specter of a putative Islamist threat was frequently invoked to gin up the Republican base.

Most tellingly, a dubious poll conducted by Gaffney's organization, the mildly named Center for Security Policy, anchored front-runner Donald Trump's sensational and xenophobic call to halt all Muslim arrivals. Trump argued, citing Gaffney's group, that "25 percent of those polled agreed that violence against Americans here in the United States is justified as a part of the global jihad."

As my colleague Philip Bump wrote last December in a post picking apart the discredited poll, there is "no reliable evidence that a large percentage of Muslims in the United States — or, for that matter, Muslims hoping to travel to the United States — support doing harm to the country or plan to commit acts of violence."

But Gaffney has a long and well-documented track record of propagating myths and conspiracy theories about Islam and Muslims in America.

In the first year of the Obama administration, Gaffney wrote an op-ed in the Washington Times that claimed "the president not only identifies with Muslims, but actually may still be one himself." He threw in a reference to Adolf Hitler duping Neville Chamberlain in Munich for some extra rhetorical oomph.

President Obama, in Gaffney's view, is the fifth-columnist-in-chief, a crypto-Muslim on a quest of "civilization jihad," bent on tearing apart the fabric of the American nation. (To be sure, numerous Republican politicians have made similar-sounding criticisms, without arguing that Obama himself is a Muslim.) In December, Gaffney accused the president of "treason" and of "playing for the other team."

And Obama's not alone.

As the Southern Poverty Law Center notes in its archive of right-wing hate groups, Gaffney is "gripped by paranoid fantasies about Muslims destroying the West from within" and "believes that 'creeping Shariah,' or Islamic religious law, is a dire threat to American democracy."

This conviction has lent itself to various claims, both grim and amusing. A supposedly authoritative report produced by Gaffney's group argued that most Muslim organizations in the United States were fronts for the Muslim Brotherhood and "as a matter of fact, hostile to the United States and its Constitution." Gaffney has invoked this laughable charge about American Muslims to push for a new era of McCarthyism, calling for Cold War-era trials of "anti-American activity" in 2011.

In 2010, Gaffney hilariously imagined that the redesigned logo of the U.S. Missile Defense Agency "appears ominously to reflect a morphing of the Islamic crescent and star with the Obama campaign logo" and was therefore a reflection of a "worrying pattern of official U.S. submission to Islam."

Gaffney has labeled his erstwhile American enemies, from Hillary Clinton adviser Huma Abedin to more moderate Republicans uncomfortable with his views, as actual members of the Muslim Brotherhood or appeasers of violent Islamism. He recently suggested that Pope Francis was "rabidly anti-American," for good measure.

According to Bloomberg View's Lake, the other members of Cruz's team -- which includes prominent neoconservatives who favor collaboration with Muslim allies -- purportedly balance out Gaffney's extremism. But they aren't free of their own polemical excesses, either.

Take Michael Ledeen, another Reagan-era official, who is now a fellow at the neoconservative Foundation for Defense of Democracies. In the buildup to the U.S. invasion of Iraq in 2003, he fumed at the European reluctance to topple Iraqi dictator Saddam Hussein.

Writing in the National Review, Ledeen argued that French President Jacques Chirac was casting "his lot with radical Islam and with the Arab extremists." Given the chaos that the war and occupation of Iraq would later unleash, and Cruz's own championing of the Middle East's secular autocrats, it was a rather unfortunate prediction.