Talk:Two-round system

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A 45% B 40% C 15%

ELECTION TWO Features candidates A and B in a "Run-off"

Advantages of a Run-Off Election

In a run-off election, the possibility of a "third party spoiler" is eliminated because no voter is forced to cast a vote for a candidate they do not favor. Here is an example:

If the US Presidential election were a run-off system, you might see this scenario. Voter 1 favors Ralph Nader. Voter 2 favors George W. Bush. Voter 3 favors John Kerry. In a regular election, assuming every voter votes their conscience, you see this result: Bush 1 Kerry 1 Nader 1 If voters vote strategically you might see this result: Voter 1 - Kerry Voter 2 - Bush Voter 3 - Kerry

Voter 3 has voted strategically, but in the process has voted against his preference. This is the heart of the spoiler issue in an electoral system. Voters who vote for a third candidate that is weaker than the top two, often prefer one of the top two candidates to the other. If they vote for the third candidate, their vote may be "wasted" because they could vote a candidate they prefer, and actually cause the candidate they least prefer to be elected by doing so. If they vote strategically, they will assure a candidate that they prefer is elected, but not the one they most prefer, which is the assumption in an electoral system.

A run-off system compensates by allowing voters to vote their first preference in the first election. In the second election, only the top two candidates are allowed to participate, so the possibility of a third party spoiler has been eliminated.

Contents 1 Requested move 1.1 Survey 1.2 Discussion 2 What happens if one candidate does receive an absolute majority? & other clarifications 3 8/9/07 changes 4 Monotonicity?

[edit] Requested move

Runoff voting → Two-round system – I know, I know, I know; all varieties of English are equally valid. However, the paragraph about terminology -- the last two sentences, complete with self-reference, are the smoking gun -- indicates that we need a move with either a redirect dab at its new location or a dab at the current location (probably unnecessary). Also see the discussion over longcase clock, a case of the inverse: the generic but uncommon name (longcase) instead of the common but non-inclusive one (grandfather). Moulder 06:56, 24 July 2006 (UTC)

[edit] Survey

[edit] Discussion

My support is for the disambig option now despite previously thinking it unnecessary. (Or maybe a generic article about the concept of "runoff voting" and how it developed, if applicable.) This is mainly to distinguish between the exhaustive system and instant-runoff voting. The trickiness of this question is why I decided to be conservative instead of bold. Moulder 22:25, 24 July 2006 (UTC)

(Re: Vegaswikian) An article about generic runoff voting, i.e. comparing and contrasting the different systems and how the term runoff applies to them, should suffice; the initial paragraph can mention the fact that the US calls two-round voting runoff voting, and then each of the systems that employs runoffs can get a mention. Moulder 22:18, 30 July 2006 (UTC)

[edit] What happens if one candidate does receive an absolute majority? & other clarifications

What happens if one candidate does receive an absolute majority? Does he/she/it win without another round of voting? If so, that needs to be stated.

What happens if candidates draw, or if you had an election which went something like this: A - 25%, B - 24%, C - 23%, D, C, E, F... - 1% each? Would C still be eliminated in the second round?

Njál 16:17, 29 April 2007 (UTC)

Most runoff systems currently in use have a rule that a candidate receiving an absolute majority wins without needing a runoff. This is not, however, required by the method.

What happens in the case of an exact tie for second place has to be settled by something external to this method. In the near-tie situation you mentioned, C would indeed be eliminated in the second round, leaving an A v B runoff. (This actually happened in the 2002 Presidential election in France, where Jean-Marie Le Pen finished in second place, less than a percentage point ahead of Lionel Jospin.)Jack Rudd (talk) 00:58, 29 May 2008 (UTC)

[edit] 8/9/07 changes

Various spelling errors in the article were corrected —Preceding unsigned comment added by 71.180.234.30 (talk) 20:37, 9 September 2007 (UTC)

[edit] Monotonicity?

I assume that runoff-voting satisfies the monotonicity criterion? Intuitively, it seems obvious that it would, but is there proof? (If the proof is trivial then in my opinion, that's all the more reason to add it to the article.) If, however, it does not in fact satisfy monotonicity, then can somebody please come up with a counter-example? 69.140.152.55 (talk) 02:36, 17 May 2008 (UTC)
It doesn't satisfy it. Here's a counter-example:

39 prefer Edwards to Roemer to Duke
22 prefer Roemer to Edwards to Duke
8 prefer Roemer to Duke to Edwards
31 prefer Duke to Roemer to Edwards

So 39 vote Edwards, 31 Duke and 30 Roemer. The top two vote-getters are Edwards and Duke, who advance to a runoff, which Edwards wins.

Now make two of the Duke voters switch to Edwards. Then Edwards gets 41 votes, Roemer 30 and Duke 29. Edwards and Roemer advance to a runoff, which Roemer wins.

This same example, incidentally, shows that runoff voting fails the favourite-betrayal criterion, although the more usual favourite-betrayal would be for voters to switch from Duke to Roemer in the first round.
Jack Rudd (talk) 00:17, 29 May 2008 (UTC)