In his IJCAI Computers and Thought Award lecture in Acapulco this summer, Tuomas Sandholm discussed election systems, and the relevance of analysing elections as multi-agent system after the 2000 Florida Presidential debacle. One system that he mentioned that intrigued me was the Irish system. As this page describes it, each voter’s ballot lists his preference order of candidates for an office. Then the votes are tallied thus:
The [ballots] are sorted according to the first preferences shown on them and the number of first preference votes recorded for each candidate notified to the presidential returning officer. That officer calculates the quota (the number of votes necessary for election). With a single position to be filled, the quota is fifty percent of the valid votes plus one. If a candidate receives a number of votes equal to or greater than the quota, he/she is declared elected.
If no candidate reaches the quota, [they] exclude the lowest candidate, transfer his/her votes in accordance with the next preference shown…. The process of excluding candidates and transferring their votes continues until one of the candidates has sufficient votes to secure election. That candidate is declared elected by the presidential returning officer.
[UPDATE: This is called Instant Runoff Voting]
What if we had this system in the U.S.? It would allow 3rd party and independant candidates to run, and people to vote for them as their first choice, without worrying that it might be better to vote for their second or third choice because otherwise someone really bad might win. In otherwords, Nader supporters could have vote for Nader with Gore as second choice, knowing that if Nader lost their votes would go to Gore. Interestingly, this system would result in more votes for third party candidates.
Democrats, if this system were in place in the Democratic primary, what would your preference be?