Explain why the single-member district system of elections tends to promote a two-party system. Also, compare the single-member district system with proportional representation systems.

What will be an ideal response?

In a single-member district system, each constituency selects only one representative for an office, on the basis of which candidate receives a plurality of the vote. This system promotes a two-party system in America. It discourages minor parties because it is, essentially, a winner-take-all contest. For example, if a minor party receives 20 percent of the vote in each congressional district, it would win no seats in Congress. Despite the fact that one in five voters voted for the minor party, the winning candidate in each district would be the major-party candidate with the larger proportion of the remaining 80 percent of the vote. In contrast, a system of proportional representation is not a winner-take-all contest. In European democracies, for example, seats in the legislature are allocated according to a party's share of the popular vote; if a minor party wins 20 percent of the vote, it receives 20 percent of the legislative seats. America's single-member district system disadvantages minor parties and, therefore, promotes a two-party system.