We examine spatial patterns of mass political participation in the form of volunteering and donating to a major statewide election campaign. While these forms of participation are predictably associated with the political and socioeconomic characteristics of the precincts in which the participants reside, we find that these statistical relationships are spatially nonstationary. High-income neighborhoods, for example, are associated with stronger effects on participation at some locations more than at others. By using geographically weighted regression (GWR) to specify local regression parameters, we are able to capture the heterogeneity of contextual processes that generate the geographically uneven flow of volunteers and contributors into a political campaign. Since spatial nonstationarity may well be a rule rather than an exception in the study of many political phenomena, social scientific analyses should be mindful that relationships may vary by location.