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Runoff voting

Runoff voting is a voting system used widely in single-seat elections throughout the world. Elections which involve runoff voting include the President of France and some elections in the United States. See also: instant-runoff voting

Table of contents
1 Voting
2 An Example
3 Potential for Tactical Voting
4 Impact on factions and candidates


In the preliminary election, voters select their preferred candidate. If one candidate reaches the election threshold (usually fifty percent plus one vote), they are declared elected. Otherwise, the top candidates (usually the top two) are placed on a secondary ballot. Whoever receives the most votes on the second ballot is declared elected.

A runoff ballot is not the same thing as having political parties holding primary elections prior to the main ballot. In a runoff ballot, all candidates are placed on the inital ballot and all voters are allowed to participate in the vote.

An Example

Imagine an election to choose the capital of Tennessee, a state in the United States that is over 500 miles east-to-west, and only 110 miles north-to-south. Let's say the candidates for the capital are Memphis (on the far west end), Nashville (in the center), Chattanooga (129 miles southeast of Nashville), and Knoxville (on the far east side, 114 northeast of Chattanooga). Here's the population breakdown by metro area (surrounding county):

Let's say that in the vote, the voters vote based on geographic proximity. Assuming that the population distribution of the rest of Tennesee follows from those population centers, one could easily envision an election where the sincere preferences would be as follows:

42% of voters (close to Memphis)
1. Memphis
2. Nashville
3. Chattanooga
4. Knoxville
26% of voters (close to Nashville)
1. Nashville
2. Chattanooga
3. Knoxville
4. Memphis
15% of voters (close to Chattanooga)
1. Chattanooga
2. Knoxville
3. Nashville
4. Memphis
17% of voters (close to Knoxville)
1. Knoxville
2. Chattanooga
3. Nashville
4. Memphis

Assuming each voter voted for their preferred city (for a more sophisticated approach, see below), the first ballot results would be as follows:

Knoxville and Chattanooga are eliminated, while Nashville and Memphis advance to the second ballot.

The voters from Knoxville and Chattanooga prefer Nashville to Memphis, so the results of the second ballot would be:

Nashville would then be declared the winner.

Potential for Tactical Voting

The runoff system violates the monotonicity criterion, as there are times when a voter can get a better result by voting tactically for a candidate other than her preferred candidate (in the first round). In the example above, voters from Chattanooga may "compromise" and vote for Knoxville (or possibly vice-versa), resulting in a second-round runoff of Memphis vs. Chattanooga, which Chattanooga would win.

In other examples, voters who prefer one of the two leading candidates may be tempted to vote for a "push-over" to make it to the second round, in order to setup a better runoff.

Impact on factions and candidates

Between each round of voting, discussion and dealing is possible; policy concessions and withdrawals can be negotiated. Accordingly, runoff votes in some form are advocated as part of most 
deliberative democracy proposals.

Other electoral reform and grassroots democracy advocates prefer instant-runoff voting, which lets larger groups participate in the process by ballot - the French participation of the whole electorate in a runoff vote is a rare exception and permits some dealing between parties who have lost and those who seek their support.

The one-ballot "instant runoff" proposals are the opposite of such 'deliberative' processes, as there is neither time nor place for explicit discussion and dealing as the power relationships become clear. Polls can take the place of early rounds of balloting, but are nowhere near as statistically valid as a formal vote.