Social media provides new platforms for political participation and ideological categorization. However, little research has been done on how party preference is related to politically active social media use. We begin with a consideration of how political participation on social media has evolved between various socio-economic and demographic groups in advanced information societies and especially in Finland. In our empirical analysis we examine the general use of social media as well as its use for political purposes with the aid of a nationally representative dataset, collected in 2017–2018 from 3,724 Finnish citizens. We argue that there are notable differences between parties when examining their supporters’ social media use for political purposes. The differences are related to the digital divides and political extremes. The results confirmed the idea that new political movements made up of younger and more educated supporters have been successful by leveraging social media. The study also revealed that the ideological gap between party supporters is greater in social media especially when examining new kinds of politics based on cultural questions, identity issues, quality of life concerns, and post-materialist values.