Andrew Myers

Security, programming languages, and computer systems


Strategic voting and the Republican primary

I’ve been interested in voting methods (algorithms for deciding who wins an election) for some time. The standard voting method (plurality) has long been criticized for being subject to vote splitting and other anomalies that cause the results of an election not to correctly represent the consensus opinion of the electorate. From the polling, the problems with plurality voting seem to be manifesting in the current Republican primary. Donald Trump is winning a plurality of the voters, yet when Republican primary voters are presented with a head-to-head, 2-person choice between Donald Trump and any one of the other top candidates, the other candidate wins. It would seem wrong to choose Trump as the candidate if most voters would prefer, say, Ted Cruz over Trump. But that is the outcome produced by plurality voting when a minority of voters prefer Trump and the votes of the remaining voters are split across three candidates. More generally, it seems problematic to choose as the winner any candidate who would lose in a head-to-head contest with another candidate — there is a majority of voters who think that second candidate is better, so most voters will be upset by the choice.

The Marquis de Condorcet identified at least a partial solution to this problem almost three centuries ago. A voting system should elect the Condorcet winner if there is one: that is, the candidate who wins pairwise head-to-head contests against each other candidate. There cannot be a majority of the voters who objects to a Condorcet winner. Condorcet voting methods are those that always elect the Condorcet winner (if there is one, which there usually is).

That’s why I implemented the first usable online Condorcet voting system, CIVS, more than 10 years ago. It gets a fair amount of use, both by open-source software organizations like Ubuntu, the Linux Foundation, and Openstack, and also by a number of universities for their own governance. CIVS is not a perfect system — there are still deep security issues to be addressed in online voting — but more than a decade of experience with Condorcet voting suggests it actually works very well.

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