Exercise 11 — Recruit a spoiler: the two-way base race¶

Generated from ex11_two_way_base.yaml — do not edit by hand. Regenerate: python STARVote_LH_tabulation_engine/tools_adam/scripts/build_yaml_pages.py.

Method: STAR (single winner) · 1 seat · Expected winner: Alba

▶ Live on BetterVoting: vote · results ↗ (election ggg7hd · test BV2197).

Scenario¶

The base case: a straight two-way race, nine voters. Alba's camp is five strong, Brett's is four — Alba wins under Choose-One (5-4), Score (25-20), and STAR (runoff 5-4). Every method agrees when there are only two names. The companion file ex11_spoiler_added.yaml adds Axl — a near-clone of Alba recruited by Brett's campaign — and asks which methods flip. (Two candidates: the finalist matrix is trivial, so show_matrix is off per house style.) Exercise: ex11_recruit_a_spoiler.md. Ballots and cast are this repo's own. Live on BetterVoting (Test ID BV2197): https://bettervoting.com/ggg7hd/results — with a Choose-One race (also Alba: two names, one verdict).

Ballots¶

Row 1 = candidate names; each later row is one voter's 0–5 scores (a N × prefix = N identical ballots).

Alba,Brett
5,0 # 5 voters: Alba's camp
5,0
5,0
5,0
5,0
0,5 # 4 voters: Brett's camp
0,5
0,5
0,5

What the engine says¶

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

--- STAR Voting Method (single winner) ---

[STAR Voting]
 Tabulating 9 ballots.
Count × Alba,Brett
    5 ×    5,    0
    4 ×    0,    5

[STAR Voting: Scoring Round]
 The two highest-scoring candidates advance to the next round.
   Alba          -- 25 -- First place
   Brett         -- 20 -- Second place
 Alba and Brett advance.

[STAR Voting: Automatic Runoff Round]
 The candidate preferred in the most head-to-head matchups wins.
   Alba          -- 5 -- First place
   Brett         -- 4
   Equal Support -- 0
 Alba wins.
   Runoff math:
     9  ballots cast
   − 0  Equal Support (no preference between the two finalists)
     ─
     9  voters with a preference  (majority = 5)
           Alba 5 (56%)  ·  Brett 4 (44%)

[STAR Voting: Winner — STAR Voting Method (single winner)]
 Alba

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

--- Runoff (Preference) Matrix ---
Head-to-head / pairwise comparison
Legend: For - Equal Support - Against
        * indicates Top 2 Finalist
               |   * Alba   | * Brett   |
-----------------------------------------
      * Alba > |    ---     |5 - 0 - 4  |
     * Brett > | 4 - 0 - 5  |   ---     |

[Condorcet Winner]
  Condorcet Winner: Alba — matches the STAR winner

[Condorcet Loser]
  Condorcet Loser: Brett — loses every head-to-head matchup

[Score Distribution] (how many ballots gave each star rating)
                Score
Candidate  5  4  3  2  1  0  | Total   Avg
Alba       5  0  0  0  0  4  |    25   2.8
Brett      4  0  0  0  0  5  |    20   2.2

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 01_STAR/05_Practice/cases/ex11_two_way_base.yaml

Exercise 11 — Recruit a spoiler: the two-way base race¶

Scenario¶

Ballots¶

What the engine says¶

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

See also¶