An electoral swing analysis (or swing) shows the extent of change in voter support, typically from one election to another, expressed as a positive or negative percentage. A multi-party swing is an indicator of a change in the electorate's preference between candidates or parties, often between major parties in a two-party system. A swing can be calculated for the electorate as a whole, for a given electoral district or for a particular demographic.
A swing is particularly useful for analysing change in voter support over time, or as a tool for predicting the outcome of elections in constituency-based systems. Swing is also usefully deployed when analysing the shift in voter intentions revealed by (political) opinion polls or to compare polls concisely which may rely on differing samples and on markedly different swings and therefore predict extraneous results.
The swing is calculated by comparing the percentage of the vote in a particular election to the percentage of the vote belonging to the same party or candidate at the previous election.
One-party swing (in percentage points) = Percentage of vote in current election − percentage of vote in previous election
For example, if a party had 41% of the vote in the previous election, and has 51% of the vote in the current election, the swing is 10 percentage points in their favour. This could be reported as +10 points.
In many nation states' media, including in Australia and the United Kingdom, swing is normally expressed in terms of two parties. This practice is most useful where most governments tend to be from an existing two-party system but other candidates do sometimes run, and is used to predict the outcome of elections in constituency-based systems where different seats are held with different previous levels of support. An assumption underlies extrapolated national calculations: that all districts will experience the same swing as shown in a poll or in a place's results. The advantage of this swing is the fact that the loss of support for one party will in most cases be accompanied by smaller or bigger gain in support for the other, but both figures are averaged into one. Employing the two assumptions allows the analyst to compute an electoral pendulum, predicting how many (and which) seats will change hands given a particular swing, and what size uniform swing would therefore bring about a change of government.
Two-party swing is calculated by taking the difference between the one-party swings of each party, then dividing by two.
In Australia, the term "swing" refers to the change in the performance of a political party or candidate in an election or opinion poll. As Australia uses the preferential voting system, swing can be expressed in terms of the primary vote (first preference vote), or in terms of the two-party-preferred or two-candidate-preferred result, which may represent significantly different values due to preference flows; i.e. a 5% primary vote swing does not necessarily represent an equivalent swing in TPP or TCP terms.
In the UK, a two-party swing (averaged model) is generally used, which adds one party's increase in share of the vote (expressed as a percentage point) to the percentage-point fall of another party, and divides the total by two.
Thus, if Party One's vote rises by 4 points and Party Two's vote falls 5 points, the swing is 4.5 points (Party 2 to Party 1).For disambiguation, suffixes such as: (Con to Lab)(Lab to Lib Dem)(Lib Dem to Con) must be added where three parties stand. Otherwise, a problem when deciding which swing is meant and which swing is best to publish arises where a lower party takes first or second, or where a party loses one of the top two places.
Originating as a mathematical calculation for comparing the results of two constituencies,any of these figures can be used as an indication of the scale of voter change between any two political parties, as shown below for the 2010 United Kingdom general election:
Swing in the United States can refer to swing states, those states that are known to shift an outcome between Democrats and Republican Parties, equivalent on a local level to marginal seats. By contrast, a non-swing state is the direct equivalent of a safe seat, as it rarely changes in outcome. The extent of change in political outcome is heavily influenced by the voting system in use.
Some websites provide a pie chart based or column-based multi party swingometer where ± x%, ± x%, ± x% and so on is displayed or can be input for three parties (or more in more plural democracies). This tool or illustration provides likely outcomes wherever more than two political parties have a significant influence on which politicians are elected.In multiparty systems exit polls frequently include a question as to voting behavior in the last applicable election. Based on those exit polls "voter migration" (where vote gains for a specific party came from and losses of another went to) analyses are published and discussed in election coverage.
In American politics, a swing state is any state that could reasonably be won by either the Democratic or Republican candidate in a statewide election, most often referring to presidential elections, by a swing in votes. These states are usually targeted by both major-party campaigns, especially in competitive elections. Meanwhile, the states that regularly lean to a single party are known as "safe states", as it is generally assumed that one candidate has a base of support from which a sufficient share of the electorate can be drawn without significant investment or effort by the campaign.
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The swingometer is a graphics device that shows the effects of the swing from one party to another on British election results programmes. It is used to estimate the number of seats that will be won by different parties, given a particular national swing in the vote towards or away from a given party, and assuming that that percentage change in the vote will apply in each constituency. The device was invented by Peter Milne, and later refined by David Butler and Robert McKenzie.
A swing vote is a vote that is seen as potentially going to any of a number of candidates in an election, or, in a two-party system, may go to either of the two dominant political parties. Such votes are usually sought after in election campaigns, since they can play a big role in determining the outcome.
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The term swing refers to the extent of change in voter support, typically from one election or opinion poll to another, expressed as a positive or negative percentage point. For the Australian House of Representatives and the lower houses of the parliaments of all the states and territories except Tasmania and the ACT, Australia employs preferential voting in single-member constituencies. Under the full-preference instant-runoff voting system, in each seat the candidate with the lowest vote is eliminated and their preferences are distributed, which is repeated until only two candidates remain. While every seat has a two-candidate preferred (TCP) result, seats where the major parties have come first and second are commonly referred to as having a two-party-preferred (TPP) result. The concept of "swing" in Australian elections is not simply a function of the difference between the votes of the two leading candidates, as it is in Britain. To know the majority of any seat, and therefore the swing necessary for it to change hands, it is necessary to know the preferences of all the voters, regardless of their first preference votes. It is not uncommon in Australia for candidates who have comfortable leads on the first count to fail to win the seat, because "preference flows" go against them.
The Mackerras pendulum was devised by the Australian psephologist Malcolm Mackerras as a way of predicting the outcome of an election contested between two major parties in a Westminster style lower house legislature such as the Australian House of Representatives, which is composed of single-member electorates and which uses a preferential voting system such as a Condorcet method or IRV.
In Australian politics, the two-party-preferred vote is the result of an election or opinion poll after preferences have been distributed to the highest two candidates, who in some cases can be independents. For the purposes of TPP, the Liberal/National Coalition is usually considered a single party, with Labor being the other major party. Typically the TPP is expressed as the percentages of votes attracted by each of the two major parties, e.g. "Coalition 50%, Labor 50%", where the values include both primary votes and preferences. The TPP is an indicator of how much swing has been attained/is required to change the result, taking into consideration preferences, which may have a significant effect on the result.
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Swing, in the politics of the United Kingdom, is a number used as an indication of the scale of voter change between two political parties. It originated as a mathematical calculation for comparing the results of two Parliamentary constituencies. The UK uses a first-past-the-post voting system. The swing is the percentage of voter support minus the comparative percentage of voter support corresponding to the same electorate or demographic.
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