Wilkerson, who is white, said the GOP "unfortunately is the bastion of those people -- not all of them, but most of them -- who are still basing their decisions on race."
Wilkerson appeared on the show to respond to Romney adviser John Sununu's suggestion -- which he later backed off of -- that Powell crossed party lines to endorse Obama because both men are black. Wilkerson said he believes Sununu's comment was "an unfortunate slip of the tongue."
Wilkerson is a retired Army colonel who served as chief of staff for Powell in the early 2000s, when Powell was George W. Bush's secretary of state. He has since been very critical of Bush, the Iraq war and the intelligence community's conclusions in the run-up to the war. He also endorsed Sen. Jim Webb (D-Va.) in the 2006 Virginia Senate race.
(For more on Wilkerson's break with his Republican colleagues, see this 2006 Washington Post story. At the time, Wilkerson's criticisms were enough to make even Powell keep his distance, despite a long and close working relationship.)
Wilkerson's comments broke the same day that a new Associated Press study revealed that a majority of Americans express "explicit anti-black views" -- even if they don't realize their prejudices.
The poll showed 51 percent of Americans expressed such views -- up from 48 percent before Obama took office -- but that the increase might be offset by rising favorable views of African-Americans.