Arguments used in favour of STV

•  STV gives voters more choice than any other system. This in turn puts most power in the hands of the voters, rather than the party heads, who under other systems can more easily determine who is elected, meaning that under STV MPs' responsibilities lie more with the electorate than those above them in their party.
•  Fewer votes are 'wasted' (i.e. cast for losing candidates or unnecessarily cast for the winner) under STV. This means that most voters can identity a representative that they personally helped to elect. Such a link in turn increases a representative's accountability.
  • It is also worth noting that when viewed as a group, politicians are largely disliked and distrusted, but when taken individually are fairly well thought of. Increasing the personal attachment between a politician and the people can thus help engender a more harmonious relationship between the voters and their representatives.
• With STV and multi-member constituencies, parties have a powerful electoral incentive to present a balanced team of candidates in order to maximise the number of higher preferences that would go to their sponsored candidates. This helps the advancement of women and ethnic-minority candidates, who are often overlooked in favour of a 'safer' looking candidate.
• STV offers voters a choice of representatives to approach with their concerns post-election, rather than just the one, who may not be at all sympathetic to a voter's views, or may even be the cause of the concern.
• Competition is generally a good thing. Competition to provide a good service to constituents is no different.
• Parliament is more likely to be both reflective of a nation's views and more responsive to them. Parties are broad coalitions, and can be markedly split on certain key issues, such as war. With only one party person per constituency to choose, the representatives elected may well not reflect the views of their electorate. Many voters in the UK general election of 2005 were faced with a dilemma, as they wanted to support a certain party, but did not want to support the war in Iraq. STV would have helped them express these views much more clearly.
• Under STV, as opposed to hybrid systems such as AMS, all MPs are elected on the same basis, thus lessening the chances of there being animosity between them.
• There are no safe seats under STV, meaning candidates cannot be complacent and parties must campaign everywhere, and not just in marginal seats.
• When voters have the ability to rank candidates, the most disliked candidate cannot win, as they are no good at picking up second-, third- and lower-preference votes.
• By encouraging candidates to seek first-, as well as lower-preference votes, the efficacy of negative campaigning is greatly diminished.
• There is no need for tactical voting.
• There is a more sophisticated link between a constituency and its representative. Not only is there more incentive to campaign and work on a more personal and local level, but also, the constituencies are likely to be more sensible reflections of where community feeling lies. For example, there is more of an attachment to the City of Leeds or the City of Manchester, than there is to, say, Leeds North East or Manchester Withington, whose boundaries have a habit of changing fairly regularly anyway.

And the counter arguments

• In some areas, such as the Scottish Highlands, STV leads to massive constituencies. This was one of the reasons cited by the Arbuthnott Commission for not recommending STV for non-local Scottish elections.
• The process of counting the results takes longer under STV, meaning that results cannot usually be declared on the same night as the vote took place.
• MPs have a habit of not liking STV on the grounds that it makes them have to pay too much attention to their constituencies. Irish politicians have twice tried to scrap STV for this reason, but both times they were defeated in the referendum.
•  Some people find voting with anything other than a solitary 'X' too complicated. This can lead to an increased amount of spoilt or voided ballot papers.
• It is expensive for political parties to campaign across the whole country, and parties are already short of funds. Parties low on cash are keener to see some form of state funding, so STV could end up costing the electorate money.
• A voting system that allows voters to rank candidates is prone to so-called 'Donkey voting', where after the first one or two choices, voters rank the rest of the field arbitrarily.
• Voters only tend to come into contact with candidates at election time, whereas people in the party know them much better. It could be argued, therefore, that a system that allows a political party to parachute its preferred candidates into safe seats is better than one that leaves the choice more in the hands of the voters.
• In large multi-member constituencies, ballot papers can get rather big and confusing.