Sounds like a complete bullshit and unplausible explanation to me.  And how can it be proven anyways?  There is no " Bradley effect", as if it were anything evenly vaguely scientific (reminds me of that idiot who wrote the book the "Tipping Point", and then never explained his thesis throughout the entire book).  But it sounds nice..   How about a more likely explanation?  Which is:   Polls are always/frequently flawed and innaccurate, and people change their minds at the last minute, sometimes seconds before entering a voting booth.   I don't think the racial issue had a significant role in the NH primary.