Book excerpt: This book examines how social media have transformed politics in established democracies. Specifically, the authors examine the influence of the unique qualities of social media on the power balance between and within parties. They present a general theory as well as an in-depth case study of the Netherlands and compare it to the US and European democracies. The authors show how and why social media's introduction leads to equalization for some and normalization for others. Additional to national politics, Jacobs and Spierings investigate often-overlooked topics such as local and European politics and the impact on women and ethnic minorities.