Can anyone explain to me what a runoff election is and under what circumstances one would be held? I am woefully ignorant - I thought you held an election, and the winner - the guy who go the most votes, um, won. Apparently, I am misguided.
Where they’re used a runoff election is held when no candidate gets a majority (50%+1) of the vote. It’s between the two candidates with the most votes. Take France for example; Sarkozy got the most votes, but that was only about 30% (12 candidates were on the ballot). Almost 2/3rds of the electorate voted against him; does it make sense for him to become President? Next week France is having a runoff where he and Royal are the only candidates on the ballot. One of them has to get a majority.
In some places, the winner has to get a plurality, that is, 50% of the votes cast plus one vote. In a field of 3 or more candidates, the top vote-getter might have only 46%. So, the top two vote-getters are pitted against each other without the other candidates. The winner takes the office.
Thank you so much!!! NOW I get it!
I’m doing a class on Chicago and its history - Chicago politics has me confused in such a way that I was up last night at 4 AM re-reading Milton Rakove’s Don’t Make No Waves-Don’t Back No Losers - I think I’m Chicago-ed out. Besides, the man uses the word milieu about a gazillion times throughout the book - come on - who USES that word? Needless to say, it is a tough read at times. 
Your mistake may have been inadvertent, but to clarify, the first situation you mention is a majority (more than 50% of a total). The second is a plurality plurality (largest single total among votes cast, but not over 50%).
Note that a run-off election need not only be between the two most popular candidates; under some electoral systems, only the least popular candidate is eliminated between rounds, meaning that if there are n candidates in an election it could take up to n-1 rounds to choose a winner. The most notable example of this is the voting system used by the International Olympic Committee to pick the Olympic host cities from the finalists.
This is how it would work in an “instant runoff” system where voters mark their first, second, third (etc.) choices. Once a voter’s first choice is eliminated, the next candidate down on the voter’s list (if still in the running) would get that vote (and so on until 50%+1 is reached). (More info)
Actually, a majority is also a plurality. A plurality is the greatest number, whether or not it is more than half:
Black’s Law Dictionary 1193 (8th ed. 2004).
True, but a plurality is not necessarily a majority. If there are multiple candidates, the winner may get a plurality (the most votes), but not a majority (less than 50%+1).
In the US and the UK, whoever gets the most votes wins (plurality), but in some other country, the winner must get a majority, too. If no one gets 50%+1 votes, then a second election is held.
This has interesting ramifications. For instance, countries where a majority is required tend to have more parties than those where only a plurality is required, which usually only has two main parties.
In many parts of the United States, runoff elections originated because there was essential one party rule. The winner of the Democratic primary in the Solid South era was going to win the general election. The runoff election allowed the voters to pick between the two highest vote getters after the minor candidates were eliminated.
My home state of Louisiana uses runoff elections. I never knew anything different growing up and they do have some advantages such as letting members of the same party run directly against one another in the open election.
“Louisiana uses a unique voting system to determine its representation in the U.S. Congress. Elections in Louisiana—with the exception of U.S. presidential elections—follow a variation of the open primary system called the jungle primary. Candidates of any and all parties are listed on one ballot; voters need not limit themselves to the candidates of one party. Unless one candidate takes more than 50% of the vote in the first round, a run-off election is then held between the top two candidates, who may in fact be members of the same party. This means that the outcome of some races might not be known until over a month later than the rest of the country.”
Perhaps according to some definitions, but not according to Merriam Webster, which I linked to above:
How often does the result of a runoff significantly differ from the pre-runoff election performance of the two candidates in question?
I assume you are just asking if the leader in the first election usually wins the final election. That depends a lot on several factors. You might have 3 Democrats and 1 Republican running in the first election. The Democrats split the votes among themselves and all come in behind the Republican (lets say the Republican gets 35% of the total votes). Now it is down to one Democrat and one Republican and the Democratic votes tend to get consolidated towards the one Democratic candidate left in the final election and the Democrat wins.
In some elections, there may be lots of candidates so having the lead with 22% of the vote may not mean much over the next highest opponent who got 19%. A runoff system may have benefited someone like George Bush the Elder. Ross Perot made a moderately strong showing in the general presidential election and it is assumed that most of Perot’s votes were at the expense of GHWB.
Candidates in both the US and the UK are, as you say, elected by a plurality, but in Canada and other parliamentary systems formation of a government requires a party to have a clear majority of the elected members. Where there are more than two parties, there may not be a majority to start with, so the leading party has to negotiate a coalition with one or more others. If the governing party or coalition loses their majority, it’s time for a new country-wide election.
Politics gets interesting that way.
By the way, a majority is NOT 50% + 1! It is simply more than half. What if you have 15 voters - a majority is 8 but 50%+1 is 8.5 votes.
Not exactly (depending on what you mean by coalition). A coalition government is generally defined to mean a government that includes members from different parties. The current Conservative government in Canada doesn’t command a majority in the House of Commons, but it can still govern by getting the support of other parties (not always the same, so it isn’t a coalition) on individual bills and motions. This is called a minority government. If they happened to lose a confidence vote in the Commons, it would be time, either to appoint a new government that commands the support of the Commons, or to call a new election. (In practice the second option is almost always what happens.)
The UK also works under a parliamentary system, so the same is true there.
OK then, let’s say that a majority is floor(50% + 1). 
We can also consider voting systems like the single transferable vote, a generalization of instant runoffs to multimember constituencies where candidates are eliminated one by one and only need to reach a certain quota (not necessarily floor(50% + 1)) to be elected. (And I believe that in some cases they can even get elected without reaching the quota.)
Runoffs are held when the law of the jurisdiction in which the election is being held so requires. In American politics, “the jurisdiction” usually means the state–even for Congressional and Presidential elections, states make the rules subject in certain circumstances to federal override.
For local elections, states may delegate rule-making authority farther down the food chain by granting “home rule” to cities, counties, or other units of government. For example, the city of Chicago, acting under its home rule power, has long determined that its aldermen should be elected in non-partisan elections with runoffs, and in the 1990’s Chicago converted to that system for its mayoralty as well. (As long as Daley continues to run, the prospect of a mayoral runoff will probably remain theoretical.)
At the state level, Louisiana and possibly Arizona and Georgia require runoffs when no gubernatorial candidate receives a majority. Mississippi and Vermont have “legislative runoff” where the legislature chooses among the top vote-getters when no one gets a majority; these are modeled after the national system in which the House of Representatives can pick the President. All other states elect by plurality.
For Congress, Louisiana elects by majority with runoff, as did Georgia until recently (I’m not sure if they changed.) A few other states required a majority in the early Republic. The predominant system has always been plurality election.
For primary elections, again, state law determines whether runoffs are held. Primary runoffs were implemented in eleven Southern states (including Oklahoma, but not Tennessee) in the early 1900’s to prevent candidates from winning office with a small plurality when the Democratic primary served as the de facto election. I’m not sure how many (if any) of these 11 states have since repealed primary run-offs.
As I mentioned before, state election laws are subject to federal pre-emption under certain circumstances. Because runoff requirements have occasionally been used to make it more difficult for minority candidates to win election, when a jurisdiction converts to runoff elections, the new rule may be subject to federal Justice Department and court review under the Voting Rights Act.
It also allows them to make sure no minority candidate actually gets elected (which was also important in the South for many years).
If there are 3 white candidates and 1 black candidate, the black candidate may get the highest vote total, but not over 50%. So in the Runoff election, the voters for all 3 candidates vote together for the remaining white candidate, and make sure no black candidate can be elected.