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One weakness of such an approach is that effective political parties are usually coalitions of factions or advocacy groups. Bringing together political forces based on a single intellectual or cultural common denominator can be unrealistic; though there may be considerable public opinion on one side of an argument, it does not necessarily follow that mobilizing under that one banner will bring results. A defining issue may indeed come to dominate one particular electoral campaign, sufficiently to swing the result. Imposing such an issue may well be what single-issue politics concern; but for the most part success is rather limited, and electorates choose governments for reasons with a broader base.
Single-issue politics may express itself through the formation of a single-issue party, an approach that tends to be more successful in parliamentary systems based on proportional representation than in rigid two-party systems (like that of the United States). Alternatively, it may proceed through political advocacy groups of various kinds, including Lobby groups, pressure groups and other forms of political expression external to normal representative government. Within a broad-based party it may be the concern of a single-issue caucus.
Very visible as it was in Western democracies in the second half of the twentieth century, single-issue politics is hardly a new phenomenon. In the 1880s, the third government of William Ewart Gladstone made British politics in practical terms single-issue, around the Home Rule Bill, leading to a split of the Liberal Party.
Groups and voters
Single-issue politics are a form of litmus test; common examples are abortion, taxation, animal rights, environment, and guns. The National Rifle Association in the United States, which has only one specific interest, is an example of a single-issue group. What differentiates single-issue groups from other interest groups is their intense style of lobbying.
The term single-issue voter has been used to describe people who may make voting decisions based on the candidates' stance on a single issue (e.g. "pro-life" or "pro-choice", support for gun rights or gun control). The existence of single-issue voters can give a distorted impression: a candidate's overall views may not enjoy the same support. For example, a person who votes for a socially liberal Republican candidate, based solely on his or her support of abortion, may not necessarily share the candidate's other views on social issues, such as gun rights or family values.
It is generally believed that single-issue parties are favoured by voluntary voting systems, as they tend to attract very committed supporters who will always vote. Through systems like instant runoff voting and proportional representation they can have substantial influence on the results of elections. First-past-the-post voting systems tend to nullify their influence, but local single-issue parties, such as Independent Kidderminster Hospital and Health Concern, which sought to reopen the Accident and Emergency unit at Kidderminster Hospital, may see more success under this voting system. This party won the Wyre Forest seat, where the hospital is located, at two consecutive general elections (in 2001 and 2005) in the United Kingdom.
In instant-runoff electoral systems which allow unsuccessful parties to designate where their votes are redistributed, single-issue parties may be formed as a way to funnel more votes to another candidate with quite different policies. For instance, in the 1999 New South Wales state election, candidate Malcolm Jones received just 0.2% of the primary vote, but achieved the quota of 4.5% required to win a Legislative Council seat after receiving preferences from a wide range of minor parties (including both the 'Gun Owners and Sporting Hunters Rights Party' and the 'Animal Liberation Party'); MLC Lee Rhiannon accused many of these parties of being nothing more than fronts.
A similar type of political party have been numerous in the Netherlands, where they are called testimonial parties. Testimonial parties are often concentrated around a specific set of principles or policies which they seek to promote without the compromises contingent on ordinary coalition politics. Examples of some successful testimonial parties are the Party for the Animals, the Reformed Political Party, or the former Pacifist Socialist Party.
In Australia, a number of single issue parties have been elected to federal and state parliaments such as the Animal Justice Party, Dignity for Disability, Australian Motoring Enthusiast Party and the Australian Sex Party.
Cannabis political parties and pirate parties which exist in a number of countries, are explicitly based around the single issues of cannabis legalization and copyright liberalisation respectively. These parties often evolve to adopt a full platform, however.