Nevertheless, there is the notorious Bradley Effect.
Yes, that's what I was addressing in my post: that the supposed motivation for the Bradley Effect (fear of being perceived as racist) doesn't make sense when people can come up with plenty of non-racist reasons for not supporting a minority candidate. And as the Wikipedia entry that you cited discusses, there's considerable debate over to its existence, and, if it exists, its extent:
"One of the more ardent critics of the acceptance of the Bradley effect as an accurate explanation for observed polling errors is Gary Langer, who serves as the director of polling for ABC News. Langer has described the Bradley effect as 'a theory in search of data.' He has argued that inconsistency of its appearance, particularly in more recent elections, casts doubt upon its validity as a theory."
Langer may be right or wrong. I'm just not going to make assumptions at this point.