A Condorcet method is an election system where voters rate their candidates in order of preference. As an example, for candidates A B and C, a valid vote can be [A > B > C], [C > B > A], [B > A > C] etc.
The vote then leads to chained preference problem which can be solved through several methods. In the above example, we have B > A > C (first two votes sums in A = B = C). Some of the votes are impossible to solve "perfectly", as known as Condorcet paradox, simply described as cyclic preferences. Each particular Condorcet method offer a different answer to this problem, but no matter what method chosen, if it respects Condorcet criteria it offers much advantages over classical votes:
- Since it rates all the candidates in a single turn, a single vote can be cast to elect a winner.
- This encourages being a good compromise candidate. For example, in a triangular scenario, the middle man can win without majority of first intention votes.
- This does not harm diversity of proposals. If two candidates A1 and A2 have similar opinion group, their supporter can elect A1 > A2 > B > C and A2 > A1 > B > C. If the opinion group is the majority, A1 or A2 can be elected without majority of first intention votes.
- It can be used as an exclusion vote, voting "against" some candidate or group
- It simply is a more powerful expression vote, allowing more analysis and involving more the voter in the outcome
Despite this, I know no large scale implementation of any Condorcet method. Although some of them are complex and require (small) computing for resolution, this really shouldn't be a problem.
What other factors are against the Condorcet method in real world elections?