This book provides an in-depth analysis of the voting criteria of selectors in Greek political parties' leadership elections, focusing on open and semi-open primaries. It examines seven multi-candidate leadership contests organised by the centre-left PASOK, the centre-right New Democracy, and the radical left SYRIZA during 2007 – 2023, from the theoretical perspective of the Stark model and the three ordered selection criteria. Drawing on polling evidence and interviews with candidates, party officials and their aides, the book argues that the model helps explain the results of Greek parties' six in seven leadership elections.