This article investigates different polarizing mechanisms—relational homophily and ideological partisanship—characterizing political communications using Twitter data collected during the 2017 Norwegian election. By combining two computational approches—partition-specific network analysis and quantitative analysis of language polarization—we can examine the linkages between the structure of interactions and political polarization. The results show that the Norwegian political Twittersphere is not made of isolated echo chambers but is structured around crosscutting communities of interaction. There are no signs that communities with higher degrees of polarization are the ones that display higher degrees of homophily. Yet, the degree of ideological polarization differs across communities and topics. Some topics, such as political hate and far right and economy and taxes, are more polarized than others.

Ideological homophily on social media has been receiving increased scholarly interest, as it is associated with the forma- tion of filter bubbles, echo chambers, and increased ideological polarization. And yet, no linkage necessarily exists between ideological homophily, echo chambers, and polarization. Despite political interactions on social media taking place to a large extent between like-minded individuals, cross-cutting interactions are also frequent. Using Twitter data, we investigated the extent to which ideological homophily, echo chambers, and polarization occur together and characterize the network of political Twitter users during the 2017 election in Norway. Despite the presence of some degree of ideological homophily, we did not find evidence of echo chambers in the Norwegian political Twittersphere during the 2017 election. And yet, the retweet network is characterized by a significant degree of polarization across ideological blocs. Our findings support the thesis according to which polarization on social media may have drivers other than the technological deterministic effect of social media affordances enhancing the formation of online echo chambers.