Which parties use simple language in their campaign messages, and do simple campaign messages resonate with voters’ information about parties? This study introduces a novel link between the language applied during election campaigns and citizens’ ability to position parties in the ideological space. To this end, how complexity of campaign messages varies across parties as well as how it affects voters’ knowledge about party positions is investigated. Theoretically, it is suggested that populist parties are more likely to simplify their campaign messages to demarcate themselves from mainstream competitors. In turn, voters should perceive and process simpler campaign messages better and, therefore, have more knowledge about the position of parties that communicate simpler campaign messages. The article presents and validates a measure of complexity and uses it to assess the language of manifestos in Austria and Germany in the period 1945–2013. It shows that political parties, in general, use barely comprehensible language to communicate their policy positions. However, differences between parties exist and support is found for the conjecture about populist parties as they employ significantly less complex language in their manifestos. Second, evidence is found that individuals are better able to place parties in the ideological space if parties use less complex campaign messages. The findings lead to greater understanding of mass-elite linkages during election campaigns and have important consequences for the future analysis of manifesto data.