This thesis explores the implications of the Internet for democracy, re-evaluating the various claims and counter-claims that have been made for the Internet's democratic potential. Based on a framework to measure democracy that emphasises popular control and political equality, it assesses whether the Internet gives a greater and more representative share of the population the opportunity to participate in the political process by focusing on use of the Internet to contact political representatives. The analysis combines secondary analysis of population surveys with original data collected in two online surveys from more than 14,000 users of successful contact facilitation platforms in the UK (WriteToThem.com) and Germany (Abgeordnetenwatch.de) that enable sending messages to representatives. The results show that in both countries the Internet in general has only marginally increased the number of people engaged in contacting. At the same time, contact facilitation platforms as specific online applications have attracted large numbers of people who have never before contacted a representative. While all online means of contacting primarily amplify traditional participatory biases, such as for gender and education, they can at least selectively engage traditionally under-represented parts of the population, for example young people or low-income groups. The processes that shape these patterns are identified by developing a basic theory of contacting and using the similarities and differences between the findings for the two countries. It demonstrates not only that participation continues to be dominated by traditional determinants that cannot be completely overcome by technology, but also that Internet applications can shape participation patterns - if designed to appropriately adapt to the context in which they operate, which is rarely the case. This highlights the need to think carefully about how online platforms can be used, building on the - albeit limited - gains identified here, to strengthen them as a means of ensuring democratic participation.