Party and PPG: Still competing principals for MPs on social media?

Competing principals theory (CPT) has been shown to be effective in parliaments when it comes to different parliamentary actions of MPs (Carey 2007). It has also proven to be a useful theoretical framework for researching MP cooperation (Bucher 2024). With the party and PPG shown to be effective in structuring these cooperative patterns in parliament (Bucher, forthcoming), the question arises whether this can also be shown in more open arenas, such as social media networks of MPs. Are parties and PPGs still the predominant principals structuring MP networks on social media? The analysis surveys networks of members of German state parliaments on Twitter/X. Using the 16 state parliaments (Landtage) as venue enables a research design that holds most cultural and societal variables stable, while introducing variance in the assemblies when it comes to the composition of parliaments and especially the parliamentary party groups. This work presents a data set of 973 Twitter accounts by 1731 members of all German state parliaments in 2021 and their subsequent Tweets and retweets. The analysis is prepared using relational inference methods, specifically a pooled temporal exponential random graph model.