Are political leaders less popular among voters than they used to be? If so, why? Many studies have mapped a decline in citizens' political trust and satisfaction with democracy, but we know less about whether leader popularity is in decline, and if so, what drives this trend. This paper examines these questions using unique data on major party leader popularity and leadership traits from the Australian Election Study collected over four decades. The results show that Australia's major party leaders have become less popular over time. We test a theoretical model which explains declining leader popularity by partisan dealignment and the role of leader integrity. The analyses show that the effect of partisanship on leader popularity has weakened over time, while leader integrity traits have become more important. These findings apply to both major party leaders that have won elections as well as those leaders that have lost elections.