Defying the current pessimistic narrative, this book challenges the prevailing assumptions that the political Left is spent, hopeful ideological discourse has collapsed and social media has corroded public debates about politics. Instead, the book argues that ideological activism remains vibrant on the Left, but there is currently no clear way of recognising and analysing this phenomenon. The book fills this gap by first defining what political social media is and then by taking a morphological approach to investigating political ideologies and revealing the ways in which interconnected concepts are arranged. It concludes by coining the term ‘proto-ideologies’ to approach the construction of concepts that generate ideologies in the making.