Condorcet

From dKosopedia

Category: Voting systems

Condorcet is a voting system named after the Marquis de Condorcet, an 18th-century French mathematician. IRV enthusiasts usually criticize Condorcet as too complicated, but it's actually simple. If one candidate can be found to defeat all other candidates in head-to-head matchups, that candidate wins. It's that simple.

A voter might rank their candidates A -> B -> C (read: A first, B second, etc). This means that in head-to-head matchups, A beats B, A beats C, and B beats C.

If a second voter had the exact same ranking, then that would mean A beats B, 2-0. A beats C, 2-0. B beats C, 2-0.

In that race, since A beats all other candidates head-to-head, A is the Condorcet winner.

In a larger election of 100 voters, you might have results like this:

A->B: 54-46
A->C: 63-37
B->C: 70-30

This means that out of 100 people, 54 preferred A to B, and 46 preferred B to A. A wins that head-to-head matchup. A also beats C, so A is the winner.

If a candidate beats all other candidates in head-to-head matchups, that candidate is called the Condorcet Winner. Voting theorists are in consensus that when a Condorcet winner exists, the election should find that candidate the winner. A voting system that awards the win to a candidate other than the Condorcet Winner is considered a flawed vote-counting method.

In 2000, all materials show that Gore was the Condorcet Winner. Gore was preferred to Nader. And in Florida, if Nader voters had been able to register their full preferences, exit polling proved that Gore was preferred to Bush overall. Therefore Gore would have beaten both other candidates in head-to-head matchups.

Plurality fails to find the Condorcet Winner in many cases. IRV also fails to find the Condorcet Winner in many scenarios.

It is possible for a Condorcet Winner to not exist. It is possible for a population to prefer A to B, prefer B to C, and prefer C to A. (For a clear example, imagine college football - Miami can beat Florida, Florida can beat Florida State, and Florida State can beat Miami.) In this case, there are many complicated tiebreaker procedures that can be followed. However, in large political elections, these kinds of cycles are extremely unlikely.

IRV-P Instant Runoff Voting - Paired

Another name for Condorcet voting is IRV-P or Instant Runoff Voting - Pairs or Paired. Since Condorcet can be seen as a race where everbody is in a run off election against everybody else with the winner of the most elections being the overall winner, the acronym IRV-P makes sense. A Condorcet purist would bristle at the notion of Condorcet being thought of as a subset of Instant Runoff Voting. However, since IRV has made inroads into common wisdom, it may be an easier concept to communicate. Further Condorcet as an English word has no natural meaning whereas Instant Runoff Voting - Paired does.

A Website for Creating your own Condorcet (IRV-P) election

Condorcet Internet Voting Service