Obama has a close association with a supporter of Louis Farrakhan:
http://www.newsmax.com/kessler/farrakhan_support/2008/01/17/65177.html For non-Americans, Louis Farrakhan is the intensely racist leader of the "Nation of Islam," a heretical American Muslim sect which believes in bizarre theories about the origins of the whites, claims to be backed by space aliens, and arms for an imaginary coming race war.
The association is indirect, but I wonder how long this will continue to be little-known, especially if Obama actually wins the nomination.