Governing parties tend to lose electoral support over time in a predictable cycle known as ‘costs of governing’. Despite its prevalence, there is limited theoretical explanation for this trend. This paper advances a competence-based theory of costs of governing. It reveals how the accumulation of policy performance information shapes public opinion about the competence of parties in government; how generalised evaluations of party competence deteriorate over time; and how these costs of governing bear on the policy issues on which governing parties are trusted – issues a party owns. The theory is supported using aggregate-level data on objective policy performance and public opinion about party competence in the US, UK, Australia and Germany. The findings have important implications for our understanding of public opinion dynamics and the alternation of incumbent and challenger parties, and for competence-based incentives in government.
