The American Conservative Union is standing by its decision to permit a panel at CPAC that includes a leading white nationalist figure, Peter Brimelow.

"CPAC is proud to have more than 150 sponsors and exhibitors this year," said spokeswoman Kristy Campbell in an email. "This panel was not organized by the ACU, and specific questions on the event, content or speakers should be directed to the sponsoring organization. Cosponsors and affiliated events do not necessarily represent the opinions of the American Conservative Union."

The group's Conservative Political Action Conference kicks off tomorrow with a host of important figures on the right, including presidential candidates and current legislators -- and with a lineup that tends to define the limits of the conservative movement. In the past, skirmishes over the inclusion of gay conservatives have been central, but this year's hottest debate appears to be over race.

Brimelow is the founder of VDARE.com, named after Virginia Dare, the first child born to English settlers in America. He's set to speak at a CPAC event called "The Failure of Multiculturalism: How the pursuit of diversity is weakening the American Identity."

The Southern Poverty Law Center describes Brimelow as a "White Nationalist" and his website as a hate site. Brimelow advocates against immigration and multiculturalism, which he has written "risks making America an alien nation."

His website publishes the work of white supremacist authors like Kevin MacDonald and Jared Taylor, a proponent of so-called "racial realism."

CPAC has faced sharp criticism since a liberal blog first noted Brimelow's presence.