British and Scottish politics are undergoing a period of tumultuous change, leading to what some scholars have labelled ‘electoral shocks’, which have altered the relative importance of the main issues explaining citizens' political behaviour. The conventional wisdom now posits that attitudes towards Scottish independence play an increasing role in structuring citizens' vote choice in Scotland. However, a longitudinal assessment of this claim is lacking. In this research, we seek to fill this gap by making use of data from 1999 to 2021, which covers every Scottish election since devolution, and providing the first‐ever systematic assessment of the strength of attitudes towards Scottish independence in explaining electoral behaviour over time. Our findings reveal a substantial increase in the importance of attitudes towards independence, which we can quantify throughout the 1999–2021 period. We conclude by discussing the implications of this for British and Scottish politics.