A white guy got elected to a black-majority congressional district. So he figured he should join the Congressional Black Caucus, following in the lead of his predecessor, Harold Ford, Jr. Afterall, he assumed, the Congressional Black Caucus centers on issues pertinent to black people (albeit from a far left perspective only). Unlike perhaps any other white congressman or senator, a majority of his staff is black, including his Chief of Staff. Answer to his request: Blacks only.
Turns out that the Congressional Black Caucus also works to defeat incumbent honkey democrats facing black challengers in the primaries. Very interesting. I wonder how its members would feel if any white legislators worked to defeat black incumbents in primaries... or if they made crackerness a requirement to join some other caucus.