Prime ministers (PMs) play a crucial role in parliamentary democracies, yet little comparative research explores how their political careers affect performance. This study uses an expert survey of 131 cabinets across 11 CEE countries from 1990-2018 to define PM effectiveness through two dimensions: domestic management and principal support.

Contrary to expectations that long political experience alone leads to better performance, the findings show party leadership background provides a significant advantage. PMs who served as party leaders achieved superior results in office compared to other career paths.

This insight offers important implications for understanding premiership selection processes.