Why and how do politicians and citizens reverse their policy preferences? To what extent do external circumstances, compared to ideological dispositions and changes in interest, drive reversals in policy preferences? Despite numerous instances of policy reversals -most recently, COVID-19 policies as governments react to new information- and human preferences for consistency, questions on why policy (preference) reversals occur, the mechanisms leading to reversals and the different types of policy reversals remain obscure. In this thesis, I explore three factors in driving reversals in policymaking and policy preferences: (i) ideology and political polarisation, (ii) trade-offs in policymaking and (iii) information provision. The first chapter of this thesis highlights the importance and relevance of reversals in policymaking, institutions and economic growth. The chapter describes and discusses gaps in the literature in relation to the different types of policy reversals. Using a simple formal model, Chapter 2 proposes a theory of policy reversals that argues that political polarisation and uncertainty over policy preferences are critical factors in policy reversals. Chapter 3 delves into the impact and experience of a political crisis, i.e., the European refugee crisis, on the policy preferences of local politicians. It examines the multidimensional policy preferences of local politicians and their willingness to support resettlement processes by conducting a conjoint experiment with 586 locally elected councillors in Greece. It uncovers that local leaders are more likely to support it if they are involved in the process and can control the frequency and intensity of local-refugee interactions. Contrary to the earlier literature, it also finds that local politicians in more exposed municipalities are no more likely to oppose hosting refugees. This finding adds important nuance to the existing theories on contact. Chapter 4 tests when local politicians are more likely to reverse their policy preferences through a survey experiment- and find that (i) ideological distance from party peers and (ii) multidimensional policy trade-offs in policy-making play an important role in generating policy reversals in the short-run. This finding has important political implications for intraparty politics. Chapter 5 investigates the impact of the COVID-19 pandemic, a crisis with economic and health consequences, on the policy preferences of citizens using a survey experiment in the US. It also looks into the impact of information provision in shifting these preferences. It finds that information provision can lead to preference reversals regardless of partisan affiliation. This finding has important policy implications for policymaking in times of crisis. Finally, Chapter 6 summarises the five chapters, their individual and collective findings and implications, and concludes. Overall, this thesis makes essential contributions to the literature on the political economy of public policy and policy opinion by exploring the drivers of multidimensional policy preferences.