  To explain the political clout of different social groups, traditional
accounts typically focus on the group's size, resources, or commonality and
intensity of its members' interests. We contend that a group's "penumbra"-the
set of individuals who are personally familiar with people in that group--is
another important explanatory factor that merits systematic analysis. To this
end, we designed a panel study that allows us to learn about the
characteristics of the penumbras of politically relevant groups such as gay
people, the unemployed or recent immigrants. Our study reveals major and
systematic differences in the penumbras of various social groups, even ones of
similar size. Moreover, we find evidence that entering a group's penumbra is
associated with a change in attitude on related political questions. Taken
together, our findings suggest that penumbras help account for variation in the
political standing of different groups in society.
