PACE voting

PACE voting is a proportional, optionally-delegated voting method for nonpartisan elections such as a city council. Essentially, it works as partially-delegated STV.

Rules
Voters are given an STV ballot, with an extra "do not delegate" checkbox.

If they vote more than one preference, or if the check "do not delegate", their vote is treated exactly as in STV.

If they vote for exactly one candidate, and do not check "do not delegate", their vote is delegated; that is, converted to an STV ballot using the public, pre-declared endorsements of their chosen candidate, and the results of the initial tally.

Before the election, each candidate has the opportunity to endorse other candidates. If a candidate chooses to endorse, they must endorse at least two other candidates.

A vote for a candidate is converted to an STV ballot by adding those endorsed by that candidate in the order of their initial vote tallies. So if X endorsed W, Y, and Z, and if the direct votes for these three were 800, 1000, and 600 respectively, a delegated vote for X would be converted to X>Y>W>Z (that is, X first, Y second, W third, and Z fourth).

Once delegated ballots are filled in, an STV (single transferrable vote) counting process proceeds as normal.

Optional rule for discouraging vote-funneling
If a candidate X gets less than 1/3 of a quota, and does not endorse at least 2 other candidates who get more than 1/2 of a quota, then X's delegated votes will not be transferred until all candidates with less than 1/2 of a quota of votes have been eliminated. During the time between when X is eliminated and when their delegated votes are transferred, their delegated votes count as exhausted for the purposes of calculating the quota. Thus, during that time, the quota for other candidates is slightly lower.

This reduces the ability of minor candidates to reliably funnel votes to a specific major candidate. Minor candidates can still be useful to a broader coalition, but have a harder time giving an unfair advantage to a single major candidate.

This rule does not unfairly punish voters who choose a minor candidate, since their votes are still eventually transferred.

Similar methods
PLACE voting: a similar system, for replacing FPTP in a partisan context (such as nationwide or state/provincial elections in Canada, US, or UK).

GOLD voting: An older, slightly more complex version of PLACE.

OL/D voting: similar to GOLD, but without the constraint of one candidate per riding, and with a slightly weaker elimination rule.

SPACE voting: a summable version of PACE; simpler for voters, but more complex in terms of vote-counting.

Proportional 3RD voting: an old version of PACE.