Four Republican presidential hopefuls are planning to attend a conference Monday organized by a man who has long promoted wild conspiracy theories. Frank Gaffney’s Center for Security Policy is hosting the so-called National Security Action Summit in Las Vegas, addresssing, the group says, border insecurity and the threats of Iran, Islamic law and global jihad.

It's billed as an event featuring “the most influential national security practitioners of our day,” and speakers include Ben Carson, Ted Cruz, Carly Fiorina and Rick Santorum.

Gaffney is known for reckless claims, from tying the Iraqi dictator Saddam Hussein to the 1995 Oklahoma City bombing (which was perpetrated by white, right-wing extremist Timothy McVeigh) to accusing Hillary Clinton’s aide Huma Abedin of being a secret agent of the Muslim Brotherhood.

The presence of so many Republican presidential canditates at an event hosted by a conspiracy theorist raises questions about the electability of those currently leading in the polls. The attendance of four candidates — including Cruz, who has taken the lead in Iowa — comes a week after front-runner Donald Trump called for a “total and complete shutdown of Muslims entering the United States” after the Dec. 2 Islamic-extremist-inspired mass shooting in San Bernardino, California. Trump is not on the schedule for the Las vegas event.

Trump pointed to a Center for Security Policy poll claiming that nearly one in four U.S. Muslims believe violence is justified against anyone who offends Islam and that a majority wants the choice of being governed by Islamic law, which prescribes the death penalty for adulterers, apostates and gays.

The poll has been called “deeply flawed” because it was performed as an “opt-in” survey, in which respondents volunteer to offer their feedback rather than being approached randomly by pollsters. According to the American Association of Public Opinion Research, surveys involving “self-selected volunteers” have no statistical validity.

Last month, Cruz -- who currently ranks second behind Trump in the RCP Republican presidential poll index –spoke at a conference in Des Moines, Iowa, hosted by Pastor Kevin Swanson, who believes that gay people should be put to death in accordance with biblical teaching.

The Southern Poverty Law Center, a civil rights group that tracks extremists, considers Gaffney “one of the country’s most notorious Islamophobes,” who believes the presence of 3 million Muslims in the United State is a threat to American democracy.