Skip to content

Symmetric centrist (47/47/3/3) — RCV-IRV: the centrist is squeezed, the poles deadlock

Generated from bv2170_pp2q4q_irv.yaml — do not edit by hand. Regenerate: python STARVote_LH_tabulation_engine/tools_adam/scripts/build_yaml_pages.py.

Method: RCV-IRV (Instant Runoff) · 1 seat · Expected winner: Avery

▶ Live on BetterVoting: vote · results ↗ (election pp2q4q · test BV2170).

Scenario

One of four races in the Symmetric Centrist election (BV2170, bvid pp2q4q; BV-confirmed). 100 voters, three candidates, ONE electorate tabulated four ways. Avery is the left pole, Blake the right pole, Casey the centrist Condorcet winner (beats each pole 53–47) — but Casey holds only 6 first choices. IRV eliminates Casey FIRST (fewest first choices), and Casey's 6 ballots split 3 to Avery, 3 to Blake, leaving Avery 50 vs Blake 50 — an EXACT TIE. The center squeeze throws out the candidate a majority actually prefers, and the two poles then deadlock.

Random tiebreak — NOT freezable, and the two engines split it differently. Because the electorate is perfectly symmetric between the poles, the final round is a genuine 50–50 tie. BetterVoting breaks it at RANDOM and this run elected Blake (frozen in the export). The LH RCV-IRV engine breaks the same tie with a stable seeded draw and lands on Avery (it does NOT honor lot_numbers — a true tie stays a tie). Neither winner is a property of the ballots: the lesson is the deadlock — once the centrist a majority prefers is squeezed out, either pole takes it on a coin flip. expected_winners records LH's deterministic-by-seed result (Avery); the frozen BV export shows Blake.

Live results: https://bettervoting.com/pp2q4q/results Companion races: bv2170_pp2q4q_star.yaml, bv2170_pp2q4q_ranked_robin.yaml, bv2170_pp2q4q_plurality.yaml. Overview page: bv2170_pp2q4q_symmetric_centrist.md

Ballots

Each row is one voter's ranking, most-preferred first (N: prefix = N identical ballots).

47:Avery>Casey>Blake
47:Blake>Casey>Avery
3:Casey>Avery>Blake
3:Casey>Blake>Avery

What the engine says

Round-by-round Sankey diagram: each candidate's votes as a band, and where the votes of an eliminated candidate transferred to.

Where the votes went. Band thickness is votes; a band leaving an eliminated candidate lands on whoever that ballot ranked next, or on inactive if it ranked nobody who was left.

The count, step by step — the rounds and how the winner is reached:

--- RCV / Instant-Runoff Voting (single winner) ---
  Symmetric centrist (47/47/3/3) — RCV-IRV: the centrist is squeezed, the poles deadlock
 Tabulating 100 ballots (ranked ballots).

ROUND 1
Candidate      Votes  Status
-----------  -------  --------
Avery             47  Hopeful
Blake             47  Hopeful
Casey              6  Rejected

FINAL RESULT
Candidate      Votes  Status
-----------  -------  --------
Avery             50  Elected
Blake             50  Rejected
Casey              0  Rejected


Winner(s) — RCV / Instant-Runoff Voting (single winner)
  Avery

Full audit — preference matrix, Condorcet, and score distribution

--- Smith Set (the generalized Condorcet winner) ---
The smallest group whose every member beats every candidate outside it —
the honest answer to "who is even in contention?".
   Smith set (1 of 3): Casey
   Outside (2):        Avery, Blake
   One member ⇒ Casey is the Condorcet winner, beating every rival head-to-head.
   RCV-IRV winner Avery is OUTSIDE the Smith set. ✗
      Every member of the set (Casey) beats Avery head-to-head, yet
      RCV-IRV elected Avery anyway. RCV-IRV is not Smith-efficient (nor
      Condorcet-efficient) — this is the shape a center squeeze leaves behind.
   More: 07_Concepts/topics/smith_set.md

Everything in one file: the _tabulated mirror (regenerated on every run; every analysis forced on).

Run it yourself:

python STARVote_LH_tabulation_engine/starvote_larry_hastings.py method_comparisons/symmetric_centrist_bv2170/cases/bv2170_pp2q4q_irv.yaml

See also

More cases in this set: bv2170_pp2q4q_plurality · bv2170_pp2q4q_ranked_robin · bv2170_pp2q4q_star