George,

Last week you queried your readers about their thoughts on instant runoffs and why we don't have them in Charlottesville when Cambridge, MA, which we all aspire to, does. I knew about the Cambridge system back in my registrar days, but I had never actually worked with such a system until recently. The Cambridge system almost defies explanation and therefore would never work here -- okay, UVA's a great school but it's not MIT or Harvard -- and it takes MIT/Harvard grads to understand how they calculate winners and losers.

The instant runoff -- also called preference voting -- system works like this:

Voters have the option to rank all the candidates on the ballot. If you get 50% plus one vote, you're in. If nobody gets that, then the low person drops off. For every ballot that had a ranking, the dropped-off loser's ballots are redistributed according to who the voters picked as number #2. Then everything is recounted to see if anyone now has 50% plus one. If no one does, the whole procedure is followed again.

Australia (and if I remember correctly Cambridge) has an added wrinkle to this method in some of its elections. Where there is proportional representation, i.e. several people elected from the same "district", there is a threshold for how many votes you need to get elected. If you have MORE than that threshold, then your overage is redistributed to the other candidates based on your voters' second-place choices. Whose ballots get redistributed? Well, in a sense, everybody's. Let's say you needed 100 votes and you got 110. That means you got 10% more than you needed. So all the second-place votes on the ballots that picked you first get redistributed, but only at a rate of 10% of the actual votes. If, on those 110 ballots, another candidate got 50 second-place votes, then that candidate would be given 5 extra votes (10% of 50).

As to using this concept in nominating conventions -- there's really no need. One of the main purposes of it is to avoid the cost of putting on another election. In a convention, the voters are all in the same place at the same time, so there's no additional cost. Plus, the pull-and-tug for a losing candidate's supporters to "join us" is part of the ritual drama of conventions. (Some of us still like ritual drama.)

As to using it in real elections -- since most of our elections are between two candidates, there's seldom the time when no one gets 50%. (Yeah, yeah, I remember our last prez election.) So it wouldn't come into play very often. The other reason we don't see more of it: it doesn't work real well with voting machines. If you're doing paper ballots, then it can all be figured out. But on machines, it's exceedingly hard (though not always impossible) to program them to allow for rankings. That's one reason we see it in the rest of the world -- because the rest of the world votes on paper ballots, not on machines.

Jim Heilman (electronic mail, March 26, 2002)