LONDON // Britons will take part in a referendum next month on proposals for the most fundamental change in the voting system in living memory.
Under the current first-past-the-post system, the winning candidate in each constituency is the one who gets the most votes, with no requirement to get an absolute majority. Under the alternative vote (AV) system, voters rank candidates in order of preference.
A candidate getting 50 per cent or more of first preference votes is elected automatically. But if no one does, the candidate with the fewest votes is eliminated and voters' second choices are allocated to the remaining candidates and the process is repeated until a candidate passes the 50 per cent mark.
The May 5 referendum on replacing first-past-the-post at general elections with AV is causing divisions within the ruling Conservative-Liberal Democrat coalition government and forging strange new alliances.
Yesterday, for instance, Prime Minister David Cameron - a Conservative opposed to AV - shared a platform with Lord (John) Reid, a Labour former home secretary normally associated with outspoken opposition to anything Tory
At the same time the 'Yes to AV' campaign was holding a rally featuring Ed Miliband, the Labour leader, and Vince Cable, the LibDem business secretary who helped forge the coalition with the Tories, rather than Labour.
Adding to this confusing mix of unlikely political bedfellows is the Communist Party and the far-right British National Party, which both support the "no" campaign.
Small wonder the British public appears confused, with the latest opinion poll on Sunday showing a six-point margin (43 per cent to 37) in favour of rejecting AV, compared to an identical margin in favour of it a few weeks ago.
Mr Cameron never wanted a referendum in the first place and only agreed to have one as part the deal with the LibDems to form a coalition government last May.
In truth, the LibDems have never really wanted AV either - before last year's election, leader Nick Clegg, who is now the deputy prime minister, branded it a "miserable" system.
But the party is now solidly behind a "yes" vote, seeing it as a small step towards the eventual goal of getting a full-blown system of proportional representation introduced.
The most glaring case of inequality first-past-the-post produced at the last election was in one English seat where the winner received a little more than 29 per cent of the vote.
Opponents of AV say including second choices in voter tallies could lead to a candidate nobody really wants becoming an MP.
At the last general election, it is estimated that results would have been different in 43 out of the 650 House of Commons seats.
Both Mr Cameron and Mr Clegg have a lot riding on the outcome. If Mr Cameron fails in the 'no' campaign, the already unhappy right wing of his party will turn on him, though an immediate challenge to his leadership is unlikely.
Should Mr Clegg see the "yes" campaign defeated, there could be open rebellion among the party faithful who already consider he has made too many concessions to their coalition partners.
Mr Cameron told Sky News at the weekend: "Whoever is on the losing side, as it were, will just have to pick themselves up and say: 'Well, the country has decided and now we have got to get on with all the things that really matter'."
But in UK politics, where being seen as a winner or a loser can determine your future as a party leader, it might not be as a simple as that.