This article examines party sorting, elite cue and ideological polarization accounts of polarization dynamics. The study tests their differing expectations about trends in redistributive ideological polarization and partisan polarization in the British case using repeated cross-section and panel data. The authors reject party sorting accounts, which require ideology to be stable and changes in party support to drive partisan polarization, because they find that ideology trends with elite polarization and that ideological change causes partisan polarization. The authors reject elite cue accounts, which maintain that it is mainly partisans' ideology that follows elite polarization, because they find virtually identical trends for initially ideologically similar non-partisans too. The study thus finds support for an ideological polarization account in which changes in elite polarization are associated with general changes in citizen redistributive ideology.