In addition, Aspen used a variation of instant runoff voting for its two at-large seats on the city council. Here is a description of the system.
Majority Voting in Multi-Seat Races with Two-Vote Instant Runoff Voting Instant Runoff Method Developed in Aspen (CO)
In May 2009, Aspen (CO) elected two at-large city council seats with an instant runoff ballot, replacing its previous two-election runoff system. Seven challengers took on two incumbents, with both incumbents losing after instant runoff tallies. Here is a description of Aspen's system.
1. How you vote: Voters rank candidates in order of choice: "1" for a 1st choice, "2" for a 2nd choice and so on. The ballot design and instructions clarified that a voter's first two rankings counted as equally weighted votes in the initial round.
2. Determining victory threshold: The total number of voters casting valid votes in the initial round of counting is determined. The victory threshold is defined as the first whole number larger than one-half this number of voters.
3. Initial count of ballots and potential for initial count winners: In the initial round a voter's first and second choice rankings are counted as one vote each. If at least two candidates reach or exceed the victory threshold, the two candidates with the most votes are elected and the count is finished.
4. If one candidate elected after initial count: If only one candidate reaches or exceeds the victory threshold on the initial count, that first-place candidate wins the first seat. An instant runoff count takes place for the second seat between the candidates in second and third. Every ballot is counted as one vote for whichever of these two candidates is ranked higher on that ballot. The candidate with the majority of votes wins. (Note: This "batch elimination" of all but the second and third candidate could be replaced with a sequential instant runoff.)
5. If no candidates elected after initial count: If no candidate reaches or exceeds the victory threshold on the initial count -- as indeed was the case in Aspen this year -- all but the top four candidates are eliminated from consideration of winning either seat. (This "batch elimination" duplicates the old system when a traditional runoff would take place among the top four candidates.) To determine the winner of the first seat, every ballot is counted as one vote for whichever of the top four candidates is ranked highest on that ballot. A sequential IRV election then takes place. To determine the second seat, the winning candidate is excluded, ballots are counted for whichever of the remaining three candidates is ranked highest on that ballot, and a second sequential instant runoff count is conducted among those candidates.
Note about this system and electing more than two seats: This variation of IRV could be used to elect three or more seats. The number of ranked candidates counted in the first round would be equal to the number of seats to be elected (first through third rankings for three seats, for example).
Evaluating Aspen's System
Although FairVote generally would recommend choice voting for such a multi-seat election, the Aspen system does a very good job in protecting the key values of IRV. Here are some observations.
1. Ranking a candidate after your initial two choices will never count against those initial choices. Furthermore, ranking a fourth choice will not count against a third choice and so on. Voter freedom is preserved in that ranking additional candidates after your top two choices does not harm your higher choices. (Those voters wanting only one vote to count in the initial count could skip their second choice and therefore never have their ballot count for two candidates at the same time.)
2. Due to the "batch elimination" and the resulting fact that no candidate finishing outside the top four in the initial count could win, it would be possible for a political force to split its vote if it runs several more candidates than opponents. This is also true of the two-election runoff system of voting that this system typically would be replacing. To avoid this relatively remote possibility, sequential elimination could be used.
3. The system is majoritarian. A slim majority of 50.1% could elect both seats – as is true of the two-election runoff system this system typically would be replacing. It is not a proportional voting system like choice voting that FairVote recommends as a first choice for multi-seat elections.