When and why do voters change their evaluation of party leaders? Voters’ evaluations of party leaders are an increasingly important determinant of electoral behaviour. Which factors influence these evaluations of party leaders? Do voters evaluate party leaders who hold the office of prime minister differently from other party leaders, and do electoral campaigns and issues change these evaluations? I use a multilevel growth model with panel data from the United Kingdom to analyse effects over time. I find that campaigns play a significant role and that voters’ stance on Brexit has a considerable time-varying effect. In addition, voters use economic performance as a valence signal for party leaders holding the office of prime minister and therefore hold them accountable for bad economic performance, especially during election campaigns. These findings show that the personalization of politics may endanger the democratic function of elections to a lesser extent than is commonly feared.