Single-issue politics involves political campaigning or political support based on one essential policy area or idea. Political expression 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. support or opposition to abortion rights, 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 their support of abortion, may not necessarily share the candidate's other views on social