The other is the fairly strong underpolling for Obama in states with large population of Mexican origin. A voter of Mexican origin (even way back) might be less willing to admit to voting for a black candidate. There also could be a social issue/religion aspect. The voter might be less willing to admit to voting for a pro-choice candidate (since most Mexican origin are Catholic, with an increasing sizable minority being Evangelical).
That effect will be the one to watch for in the future. The traditional Bradley Effect may be decreasing, while this "Reverse Bradley Effect," "McCain Effect" "Mexican-American Effect" might be increasing. And it looks like more of a voting effect than a polling effect.
It could also be that pollsters undersampled Hispanics because Hispanic turnout in the past has been very low, or because they bought into the nonsense from the Hillary campaign and others about how Hispanics wouldn't vote for a black man.
