> 2004 peter hart survey done for afl-cio had white male union
> members voting 21% pts higher for kerry, in contrast to white
> males as a whole voting 18% pts higher for bush (white women
> union members voted 35% pts higher for kerry
> over bush)... mh
That requires a caveat that these figures may simply be an effect of other divisions that coincide with union membership (regional, urban/rural, north/south, blue/red states etc.), or simply be an artifact of self-selection (i.e. liberals are more likely to vote for Kerry and be a union member).
To rule out the spuriousness of the first kind, you would need to control for known geographic differences in voting patterns, which in turn requires a rather large sample (perhaps even of the magnitude of 50,000 used by the census). Does the survey you refer to allow that? I'd be interested to see the effects of such controls, if it does.
To rule out the spuriousness of the second kind, you need a longitudinal panel data for individuals to show what comes first, union membership or voting Democratic. Such data may not be available for individual elections, but they surely must exist for general party preference. This is not really my field so I do not know what data are available, but can somebody with expertise in that field shed more light on this subject?
Wojtek