User:Psephomancy/2D election simulation examples

From electowiki

This is an example simulation of an election on a 2-dimensional political spectrum (such as the Political Compass, Nolan chart, Pournelle chart, etc.; it doesn't matter what the actual axes are.)

There are 3000 voters (black dots), 3 candidates (colored dots), and voters vote honestly, supporting the candidates who are most similar to them ideologically (nearest distance).

  • C (green) is a partisan candidate on the right
  • A (blue) is another partisan candidate, this time on the left
  • B (orange) is a moderate candidate, and the best representative of the average voter

FPTP

C wins under first-past-the-post voting, since A and B split the votes of the left wing of the electorate. (If A hadn't run, then B would have won. If B hadn't run, then A would have won. But since they both ran in the same election, C won instead.)

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IRV ("RCV") / Exhaustive Ballot

A wins under Instant-Runoff Voting ("Ranked-Choice Voting"), after B is eliminated for not having enough first-preference votes, leaving A and C. (A is slightly closer to the center, so more people in the center support A over C.)

First round is the same as plurality:

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Second round after B is eliminated:

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Top-two runoff / Open primary / Contingent Vote

A wins under top-two runoff or an open primary. A and C have the most votes and proceed to the runoff. (None of the candidates gets over 50% in the first round.) A is slightly closer to the center, so more people in the center support A over C in the runoff.

First round is the same as plurality:

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Second round after B is eliminated:

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Score

B wins under Score Voting (with normalized ballots), as they are the highest-rated overall by the voters. (Dark-colored voters gave that candidate a maximum score, white-colored voters gave them a minimum score.)

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Condorcet

B also wins under Condorcet methods, as B would beat both A and C in head-to-head elections.

A vs B:

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B vs C:

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STAR

B also wins under STAR Voting. The first round is the same as Score, so the top-two winners are A and B (since A is slightly closer to the center than C):

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B is then preferred over A by a 66% majority.

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