Favorite betrayal (RCV-IRV) — BETRAY: 2 Left voters rank their favorite SECOND, and win¶

Generated from bv2228_bgcmxx_betray_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: Center

▶ Live on BetterVoting: vote · results ↗ (election bgcmxx · test BV2228).

Scenario¶

The honest election (fb_irv_honest) exactly, with ONE change: just 2 of the 12 Left voters betray their favorite — they rank Center FIRST and Left second (Center > Left > Right) to keep the compromise Center from being squeezed out. Now Left has the fewest first-choices (10) and is eliminated instead of Center; Left's ballots flow to Center, and CENTER wins the final 21-13. By ranking their true favorite second, those 2 voters got a far better outcome (their second choice instead of their worst). That is "favorite betrayal": under RCV-IRV, honesty is not always safe — putting your favorite first is only safe when they're either very strong or have no chance at all. STAR and Ranked Robin remove the incentive: see fb_star_honest, where the HONEST ballots already elect Center. Concept: favorite_betrayal_voting_301.md.

Ballots¶

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

10:Left>Center>Right
6:Center>Left>Right
5:Center>Right>Left
13:Right>Center>Left

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) ---
  Favorite betrayal (RCV-IRV) — BETRAY: 2 Left voters rank their favorite SECOND, and win
 Tabulating 34 ballots (ranked ballots).

ROUND 1
Candidate      Votes  Status
-----------  -------  --------
Right             13  Hopeful
Center            11  Hopeful
Left              10  Rejected

FINAL RESULT
Candidate      Votes  Status
-----------  -------  --------
Center            21  Elected
Right             13  Rejected
Left               0  Rejected


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

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): Center
   Outside (2):        Left, Right
   One member ⇒ Center is the Condorcet winner, beating every rival head-to-head.
   RCV-IRV winner Center is INSIDE the Smith set. ✓
      Not guaranteed — RCV-IRV is not Smith-efficient — but it holds here.
   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/favorite_betrayal_irv/cases/bv2228_bgcmxx_betray_irv.yaml

Favorite betrayal (RCV-IRV) — BETRAY: 2 Left voters rank their favorite SECOND, and win¶

Scenario¶

Ballots¶

What the engine says¶

Full audit — preference matrix, Condorcet, and score distribution¶

See also¶