Single-member

Gerrymandering

Single-member districts enable gerrymandering, the practice of manipulating district boundaries to favor one political party. Whereas proportional multi-member districts ensure that political parties are represented roughly in proportion to the share of the vote they receive, in single-member districts the entire district is represented by a single politician, even if a sizeable minority (or even a majority, in the case of plurality voting) of the electorate votes for candidates from other parties. This enables political parties to rig elections in their favor by drawing districts in such a way that more districts are won by their party than their proportion of the overall vote would dictate (in the 2018 Wisconsin State Assembly election, for example, the Republican Party won 45% of the popular vote but 64% of the seats, due in part to gerrymandering).