Recent work has suggested that when voters are less partisan, legislators engage in more personal vote-seeking. This has potentially important implications, given the widespread decline of partisanship in many countries, and the well-noted consequences of personal vote-seeking for policy-making, election results, and accountability. However, existing tests of this argument use either aggregate-level measures of partisanship, or constituency-level proxy measures. We thus lack direct evidence linking constituency-level partisan dealignment to MPs’ parliamentary behaviour. To address this lacuna, this paper uses multilevel regression and poststratification (MRP) to produce new estimates of constituency-level partisan dealignment in the UK between 2010 and 2017. I then test the relationship between these estimates and – as an indicator of personal vote-seeking – MPs’ constituency focus in parliamentary speeches. I find that when MPs represent a less partisan constituency, they talk more about that constituency in parliament. This offers new evidence that local voters’ attitudes to political parties shape the way their elected representatives behave.