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 partisanship to MPs’ parliamentary behaviour.