The process of adapting electoral districts under majoritarian rules (MR)
matters for parties’ preferences for the introduction of proportional representation
(PR). Using the case of Switzerland, we demonstrate that gerrymandering,
that is, the manipulation of electoral districts for partisan
gain, was both substantial and effective in protecting the Liberals’ dominant
political position at federal level. Second, we show how insurgent
parties successfully pushed for the adoption of PR to end the practice of
partisan gerrymandering. Together these findings demonstrate that electoral
markets for voters are not set in stone but endogenous to parties’
preferences for electoral system choice. Electoral engineering strategies
under MR, and in particular the process of adapting electoral districts, are
key determinants of parties’ position on electoral system choice.