The talk describes a web GIS application based on open source geospatial software components that was built for the Obama Campaign during the 2008 US presidential election. The goal of the application was to support the work of campaign field organizers in battleground states for voter targeting and prioritization purposes. Technically the application was hosted on an Amazon EC2 server running an Ubuntu (Linux) operating system, Apache 2 HTTP Server, PHP server side scripting and included three main building blocks of the web GIS: a spatial database (PostGIS), a map rendering engine (MapServer), and a mapping framework which supplies the map viewer (OpenLayers). The initial application was set-up for the state of Indiana as a template and was used as a model to build similar applications for other battleground states to follow. The idea was that all battleground states have their dedicated website and data sources, but share the server applications and GIS components. Data relevant to the Campaign such as voter registration percentages, voter persuasion rates, and vote activities of prior elections were mapped on voting district (precincts) level. In addition information about individual voters and their likely candidate of choice, along with a variety of base layers were published as Web Map Services (WMS) via MapServer. Many of the relevant election data in the PostGIS databases were then updated by the campaign on a daily basis. Spatial data from WMS were then draped over background layers such as Yahoo or Google base maps in the OpenLayers map viewer. The template-oriented approach worked well for the campaign and later was rolled out to about a dozen battleground states. The project illustrates how powerful interoperable OS GIS components can be, even with minimal customization and on a low budget: http://www.geoconnexion.com/uploads/open_sources_18_intv8i3.pdf