Skip to content

ranked_choice

Jump to bottom
cwulfman edited this page Aug 28, 2022 · 1 revision

Ranked-Choice Voting

What is Ranked-Choice Voting?

The NIST Glossary defines ranked-choice the following way:

A vote variation:

  • which allows each voter to rank contest options in order of the voter’s preference,
  • in which votes are counted in rounds using a series of runoff tabulations to defeat contest options
  • with the fewest votes, and,
  • which elects a winner with a majority of final round votes in a single-winner contest and provides proportional representation in multi-winner contests.

Defining an RCV Contest in NIST-1500-100

The Contest class includes a VoteVariation attribute, which is used to indicate the rules or contest-decision algorithm to be used when compiling the results of a contest. In the US, most contests are determined by plurality: each voter may cast a single vote, and the candidate with the most votes wins. Such a contest might be represented in NIST-1500-100 like this:

{
  "@type": "ElectionResuts.CandidateContest",
  "@id": "mayoral_contest",
  "OfficeIds": ["office_mayor"],
  "VoteVariation": "plurality",
  "VotesAllowed": 1,
  "ContestSelection": [
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_1",
      "CandidateIds": ["amy_alpha"]
    },
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_2",
      "CandidateIds": ["betty_beta"]
    },
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_3",
      "CandidateIds": ["gary_gamma"]
    },
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_4",
      "CandidateIds": ["david_delta"]
    }
  ]
}

The definition of a contest using ranked-choice to calculate outcomes is almost exactly the same:

{
  "@type": "ElectionResuts.CandidateContest",
  "@id": "mayoral_contest",
  "OfficeIds": ["office_mayor"],
  "VoteVariation": "rcv",
  "VotesAllowed": 3,
  "ContestSelection": [
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_1",
      "CandidateIds": ["amy_alpha"]
    },
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_2",
      "CandidateIds": ["betty_beta"]
    },
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_3",
      "CandidateIds": ["gary_gamma"]
    },
    {
      "@type": "ElectionResults.CandidateSelection",
      "@id": "selection_4",
      "CandidateIds": ["david_delta"]
    }

  ]
}

The candidates in a ranked-choice contest are no different; only the VoteVariation and the VotesAllowed change. In this contest, voters may make three selections; the designer of the ballot is responsible for presenting the options in such a way that voters may indicate their first, second, and third choices.

BallotStyles for RCV Contests

A BallotStyle for an RCV contest is no different from a BallotStyle for a plurality contest:

{
  "@type": "ElectionResults.BallotStyle",
  "OrderedContent": [
    {
      "@type": "ElectionResults.OrderedContest",
      "ContestId": "mayoral_contest",
      "OrderedContestSelectionIds": [
        "amy_alpha",
        "betty_beta",
        "gary_gamma",
        "david_delta"
      ]
    }
  ]
}

The NIST-1500-100 Specification provides no guidance to the ballot designer on how to present these selections to a voter so that the proper number of ranked selections may be made and recorded. Such a ballot designer would be well advised to study the NIST-1500-103 specification for Cast Vote Records (CVRs), particularly section 5.8.1, which provides an example of an RCV contest and the way it would be represented.

Clone this wiki locally