A data geek could work with the National Election Studies <http://www.umich.edu/~nes/>. They're the best we've got, and they go back a long way. Doug <<<<<>>>>>
nes dates to '48, prior to that there is some gallup election data going back to 36 which includes union member - divided into afl & cio - votes for dem & rep prez candidates, nes surveys ask about union households vote choice, not union member vote choice, and nothing re. union member/race/vote choice combo (i've been working with nes stuff since early '70s undergrad days)...
i've never seen any data from any longitudinal survey research that begins to get at questions that yoshie asked (to which my previous post in this thread - indicating absence of availability of such data - was a response)... mh...