Mickey Kaus and Polipundit have already contemplated the reverse Bradley Effect in Iowa. I wonder if there might be a different kind of reverse Bradley effect, this time in South Carolina. Is it possible that some black voters would tell pollsters they support Hillary (or that they're undecided) because they don't want to sound like they're voting mainly out of racial solidarity, even though they actually intend to vote for Obama? If so, you could have a reverse Bradley effect, in which polling understated support for the black candidate in a primary with a large African American population (i.e., Obama in South Carolina).
More importantly, has anyone (commenters, this means you) ever heard of such a thing? I know that, in his U.S. Senate primary in 2004, Obama ended up winning close to 90 percent of the African American vote despite posting only a slight majority among blacks a few weeks earlier. But that's not the same as a Bradley Effect, where the actual outcome departs significantly from the final polls...
--Noam Scheiber