A single-member district is an electoral district that elects exactly one representative, usually by plurality vote. In AP Gov, it's the structural reason the U.S. has a durable two-party system: only the top vote-getter wins, so third parties rarely convert votes into seats.
A single-member district is exactly what it sounds like. The country is carved into districts, and each district sends one (and only one) representative to the legislature. The U.S. House works this way: 435 districts, 435 winners, no second-place prizes. Pair that with plurality voting (whoever gets the most votes wins, even without a majority) and you get a winner-take-all system where finishing second gets a party nothing.
That "nothing for second place" math is why the term matters so much in AP Gov. A third party could win 15% of the vote in every district in America and still hold zero seats, because it never came in first anywhere. Voters know this, so they tend to stick with one of the two major parties rather than "waste" a vote. Political scientists call this pattern Duverger's Law, and the AP exam loves it: single-member, winner-take-all districts tend to produce two-party systems.
Single-member districts live in Unit 5 (Political Participation), where the CED asks you to explain structural barriers to third-party and independent candidate success. The winner-take-all nature of single-member districts is the number one structural barrier you should name. It explains why minor parties like the Libertarians or Greens win votes but not offices, why the Democratic and Republican parties have dominated for over 150 years, and why major parties can absorb third-party ideas without losing power. The concept also connects backward to Unit 2, since House districts are the units that get redrawn (and gerrymandered) after each census. If an FRQ asks why the U.S. has two parties while many European democracies have five or six, single-member districts are the answer.
Keep studying AP Gov Unit 5
Plurality Voting / Winner-Take-All System (Unit 5)
Single-member districts and plurality voting are two halves of the same machine. The district says "one seat," plurality says "most votes takes it," and together they create winner-take-all elections where 49% of the vote can earn 0% of the representation.
Proportional Representation (Unit 5)
This is the contrast case the exam expects you to know. In proportional systems, a party winning 20% of the national vote gets roughly 20% of the seats, so small parties survive. In single-member districts, that same 20% likely gets nothing.
Gerrymandering (Units 2 & 5)
Single-member districts have to be drawn somewhere, and whoever draws the lines can pack or crack voters to manufacture safe seats. Gerrymandering only works because each district produces exactly one winner.
Electoral College (Unit 5)
Most states apply the same winner-take-all logic to presidential elections, awarding all their electors to the statewide plurality winner. That's why third-party presidential candidates can win millions of votes and zero electoral votes.
Multiple-choice questions usually test the cause-and-effect chain rather than the bare definition. Expect stems like "Which electoral system feature most directly creates a structural barrier for third-party candidates?" or questions asking what Duverger's Law predicts winner-take-all systems produce (answer: two dominant parties). You may also see comparison questions distinguishing single-member plurality districts from proportional representation, where seats are allocated by national vote share. On free-response questions, this term does explanatory work. The 2018 SAQ on parties seeking to win elections is the kind of prompt where citing single-member, winner-take-all districts as the structural reason for two-party dominance earns the point. Be ready to do three things: define it, link it to the spoiler effect and strategic voting, and contrast it with proportional representation.
Single-member districts award one seat per district to the candidate with the most votes, so losing parties get nothing. Proportional representation awards seats to parties based on their percentage of the total vote, so a party with 25% support gets about 25% of the seats. The first produces two big parties; the second sustains multiparty systems. AP Gov MCQs frequently make you pick which system explains which outcome.
A single-member district elects exactly one representative, which is how all 435 U.S. House seats are filled.
Combined with plurality voting, single-member districts create a winner-take-all system where second place earns zero representation.
Duverger's Law says single-member, winner-take-all districts tend to produce two-party systems, which is the standard AP explanation for Democratic and Republican dominance.
Single-member districts are the main structural barrier to third-party success, since minor parties can win millions of votes nationally but no seats.
Proportional representation is the opposite system, allocating seats by vote percentage, which is why multiparty systems thrive in many European democracies.
Because each district has one winner, redistricting and gerrymandering directly shape which party controls each seat.
It's an electoral district that elects one representative, usually by plurality vote. The U.S. House uses 435 single-member districts, and AP Gov treats this setup as the structural foundation of the American two-party system.
Because only the top vote-getter in each district wins anything. A third party can earn 15-20% of the vote everywhere and still win zero seats, which discourages voters from supporting it and donors from funding it.
Single-member districts give one seat to the plurality winner in each district, while proportional representation distributes legislative seats based on each party's share of the total vote. PR lets small parties win seats; single-member districts shut them out.
Not exactly, but it runs on the same winner-take-all logic. Most states award all of their electors to the candidate who wins the statewide plurality, so finishing second in a state earns a candidate nothing, just like in a House district.
Duverger's Law is the observation that single-member, winner-take-all electoral systems tend to produce two-party systems. It shows up on AP Gov multiple choice as the link between U.S. electoral rules and Democratic-Republican dominance.
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