Liberal Democrat leader Nick Clegg has criticised the current electoral system because it is possible for a party to win the election while getting fewer votes than another party.
How is it possible?
Consider this simplified example of an election involving three parties competing in three seats, each of which has 30 voters.
A simple first-past-the-post election
Party A has won the election despite receiving fewer votes than the other two parties.
It is possible because there is no value placed on votes in seats that you do not win, so the 11 votes that party C received in seat 2 were effectively wasted.
There is also no value placed on having a bigger majority, so gaining extra support in a constituency that you already hold does not help your party very much.
This is a problem for parties that have some support in a lot of constituencies, but less concentrated support.
In 2005, the Liberal Democrats received 22% of the votes but only won 62 seats, which was less than 10% of the seats in the House of Commons.
In the 1951 general election, Winston Churchill's Conservatives won 26 more seats than Clement Attlee's Labour Party despite having received about 250,000 fewer votes.
The electoral system means that opinion polls that aim to reflect percentage support throughout the country may be misleading, because what matters is not the total proportion of votes won but the amount of concentrated support that wins seats.
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