In some circumstances, politicians set about altering the composition of their electorate with a view to increasing their chances of being re-elected. A hypothesis along these lines is formulated in the context of local elections and residential mobility. Although the hypothesis is general, an assessment of its validity implies auxiliary assumptions related to a specific spatio-temporal context. That is done with reference to conditions prevailing in post-war French metropolitan areas. In the empirical part of the paper, some of the implications are submitted to tests on demographical and political data. On the basis of the tests, and although alternative explanations of the findings are possible, the hypothesis can be said to be corroborated.