The Economist explains

How British elections work

By R.C.

ON MAY 7th Britain is holding a general election to choose a new government. The country has one of the oldest electoral systems in the world, which has evolved gradually over the course of several centuries. But how does it work today?

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The country is a constitutional monarchy, so electors will be voting solely for their local members of parliament (MPs) rather than directly for a head of state (such as the president in America). The new prime minister will be the man or woman who can command a majority of MPs in the House of Commons, and he or she will then be sworn into office by the unelected head of state, Queen Elizabeth. One of the most important features of the Westminster model, as it’s often called, is the “first past the post” system. Most countries now have some form of “proportional representation” (PR) system, whereby the number of legislators in a parliament more or less reflects the number of votes cast for each political party. In Britain, however, it’s all about the number of MPs rather than voters.

There are 650 parliamentary seats up for grabs, the vast majority of them (533) in England, the biggest and most populous part of the United Kingdom. Scotland has 59 seats, Wales 40 and Northern Ireland 18. On average, each seat corresponds to 92,000 people, or 68,000 electors. Traditionally, under the first past the post system, parties have only needed to get a bit over a third of the popular vote to secure a majority of MPs and so form a government. Tony Blair’s last great election victory, in 2005, was achieved with only 35% of the popular vote. This was nonetheless enough to give him a majority of 64 seats in parliament. As prime minister, Margaret Thatcher twice won enormous parliamentary majorities of over 100 in general elections, but never won more than 42% of the popular vote. The system has thus favoured strong, one-party rule, and so a strong executive. There has been little need for the endless horse-trading with minority (and often minuscule) parties that characterise the German or Israeli PR systems.

That may now be changing. This is mainly because the smaller parties are taking an ever bigger share of the popular vote, and so might now begin to win more parliamentary seats. At the last election in 2010 the Scottish National Party (SNP), the Green Party and the UK Independence Party (UKIP) amassed just 6% of votes together. This gave them just one (Green Party) seat in England, and six, all SNP, in Scotland. This time, however, all these parties have been polling over 5% each—the SNP considerably better in Scotland, where they are expected to wallop the Labour Party for the first time in history. Thus the chances of a coalition government should be even greater this time round than in 2010, when the Conservative leader David Cameron came up 20 seats shy of an overall majority, and so had to form a coalition government with the Liberal Democrats. On present predictions it seems certain that once again neither Labour nor the Conservatives will be able to command an overall majority. But now it could be the SNP's turn to wield influence in forming the next government, much as the Liberal Democrats did before. Even UKIP, if it picks up a few seats, could play a role in coalition haggling. Certainly, thumping majorities and neat results are beginning to look like relics of a bygone era.

Dig deeper:
Why Britain's two-party system is under pressure (February 2015)
One of the eternal facts of British politics is no longer true (February 2015)

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