Nationalization, network structure and partisan polarization

Existing research has explored the link between nationalization of politics in the US and increasing partisan polarization. However, no study heretofore has systematically examined how different social network structures interact with increasingly nationalized partisan interactions to result in sustained partisan polarization. Results from analyses of a number of different network specifications, different network sizes, different average degrees and different nationalization levels show that the level and speed of polarization are governed by two interchangeable channels of partisan exposure — the volume of local connectivity (average degree) and the strength of the national signal (nationalization), while a comparison between a Facebook network and four theoretical networks reveal that mixing speed (algebraic connectivity) and community structure (modularity) shape the durability of polarization. Therefore, polarization is best understood as the emergent product of nationalization and connectivity, with network structure a genuine but second-order contributor whose influence is greatest when nationalization is low.