RCV-IRV variants — the sequential-elimination family

"Instant runoff" names a family: methods that count ranked ballots by eliminating candidates one at a time. They differ in exactly one design choice — which candidate is eliminated each round — and that single choice changes the method's properties. (One page here varies a different dial: block preferential voting keeps Hare's elimination rule exactly and repeats the whole count once per seat.)

Start here → Which RCV-IRV? — Hare and the Other Sequential-Elimination Methods

The pages

• Which RCV-IRV? — the family overview: Hare (the US "RCV") and its siblings, compared on one table.
• RCV-IRV (BTR) — Bottom-Two-Runoff — eliminate the pairwise loser of the bottom two; the variant that becomes Condorcet-compliant.
• RCV-IRV (Coombs) — eliminate the most-hated, not the least-loved.
• RCV-IRV (Baldwin & Nanson) — Borda-elimination hybrids.
• RCV-IRV (Contingent & Supplementary Vote) — instant runoff compressed into one round, and what the rank cap discards.
• RCV-IRV (Block Preferential) — instant runoff run once per seat: the multi-winner variant that is majoritarian, not STV.
• RCV-IRV with equal ranks — the one page here that varies the ballot rather than the elimination rule: Approval-IRV and Split-IRV, the two ways to let a voter mark a tie.

The family-tree diagram source lives in RCV_methods_family_tree.mermaid.