How and why party position estimates from manifestos, expert, and party elite surveys diverge: A comparative analysis of the ‘left–right’ and the ‘European integration’ dimensions

This paper examines the validity of three approaches to estimate party positions on the general left-right and EU dimensions. We newly introduce party elite data from the comprehensive IntUne survey and cross-validate it with existing expert survey and manifesto data. The general left-right estimates generated by elites and experts show a higher congruence than those derived from party manifestos; neither measure clearly materializes as more valid regarding EU positions. We identify which factors explain diverging estimates. For instance, disagreement among experts has greater impact than their mere number. The substantial centrist bias of the manifesto estimates persists even when alternative documents are used to substitute manifestos. Low response rates among elites have no systematic detrimental effect on the validity of party position estimates.