The most common form of RCV for single-winner offices is instant-runoff voting.
Two details that matter:
RCV can change outcomes because it uses more information from each voter than a single mark—especially about who is acceptable as a backup choice.
In a single-winner RCV election with no first-round majority, what triggers a ballot to move to another candidate in later rounds?
A ballot transfers when its currently counted candidate is eliminated, and it transfers to the next ranked candidate who is still eligible. Random reassignment is a common misconception because people imagine the system ‘redistributes’ votes arbitrarily—but it follows the voter’s rankings. Polling has nothing to do with the count; transfers are purely rule-based. Ranking every candidate can prevent exhaustion, but it isn’t required for a ballot to transfer at least once.
Why can RCV produce a different winner than plurality even if the same voters participate?
RCV can change the winner because the elimination-and-transfer process rewards candidates who can gain support from voters whose first choices drop out. It’s a common assumption that the first-round leader must win, but under RCV a candidate can lead initially and still lose if they can’t attract enough second/third-choice support. RCV does not weight ballots based on how many ranks you fill in (though leaving ranks blank can lead to exhaustion). And it doesn’t compute an ‘average ranking’—it’s a sequence of runoffs using ranked backups.