Data collected from internet platforms provide researchers with new insights into human behavior online. As stated by the Computational Social Science (Lazer et al. 2009) and Digital Methods (Rogers 2009) research programs these data also offer more general insights. Recently the microblogging service Twitter has become a popular tool for users to comment on political campaigns. The automatic collection of these messages is possible since users usually include a campaign specific #keyphrase. Users not only comment on politicians or parties but also post links to news articles and blog posts. This allows researchers to map campaigns: The frequency of twitter messages containing a campaign specific #keyphrase allows researchers to map the intensity of a given campaign over time; the frequency of words contained in campaign specific twitter messages allows researchers to map topics dominating specific campaigns during specific time frames; links to news content allow researchers to understand what elements of the media environment dominate the public discourse. We demonstrate this potential by analyzing twitter messages commenting on one of the most controversial recent public discussions in Germany, Stuttgart 21. The basis for this analysis are twitter messages by the 80.000 most active German twitter users collected through the Twitter API during 2009. Using all messages containing the keyphrase #21 we map the development of the public discussion with regard to message frequency over time, dominating keywords in campaign specific messages, and media content prominently linked in campaign specific messages.
