One possible way to test the extent to which a given group is predominantly politically liberal, white, and middle class is to look at that group’s attitudes towards environmentalism:
“The evidence suggests that most mainstream environmentalist groups have traditionally had little interest in issues faced by poor, minority, urban people…. Under the circumstances, it is hardly surprising that at least some observers have had harsh words for mainstream environmentalism. For example, in his book Environmental Quality and Social Justice in Urban America, James Noel Smith has argued that mainstream environmentalism is ‘a deliberate attempt by a bigoted and selfish white middle-class society to perpetuate its own values and protect its own lifestyle at the expense of the poor and underprivileged.’ A similar view was expressed even earlier by Richard Hatcher, then mayor of the city of Gary, Indiana. ‘The nation’s concern with the environment,’ Hatcher said, ‘has done what George Wallace had been unable to do: distract the nation from the human problems of black and brown Americans’ (“The Rise of Anti-Ecology,’ 1970)….” [Environmental Justice: A Reference Handbook, David E. Newton (Santa Barbara, Calif.: ABC-CLIO), pp. 15-16.]
If a group is predominantly concerned with the siting of hazardous waste disposal sites and incinerators, heavy metals in the soil, high cancer rates due to environmental toxins, environmental hazards concentrated in communities of color, food security, etc., you can safely predict that that group has few liberal white middle class people in it. If, on the other hand, a group is predominantly concerned with carbon footprints and alternative energy, preservation of non-local wildlife and natural spaces, “locavore” issues, and the like, it is more probable that such groups are dominated by liberal white middle class people. (And if a group believes that the best solutions to hypothetical environmental problems will be created by businesses and the free market, there’s a good chance that those groups are dominated by more conservative white middle class people.)