Scenarios for Britain's uncertain election
Britain's general election on Thursday is expected to be the closest for decades, with the outcome deeply uncertain.
Latest polls suggest the main opposition Conservatives will come first, with the governing Labour Party second and the Liberal Democrats third -- although the Lib Dems surged into second place temporarily during the campaign.
The quirk of Britain's first-past-the-post system is that the party with the greatest proportion of votes does not automatically win the greatest number of seats in the House of Commons.
Britain is accustomed to forming a government from the party which wins an overall majority of seats, but polls show this is unlikely in this election, producing a hung parliament for the first time since 1974.
These are four of the most likely scenarios:
1: The Conservatives win an absolute majority:
This is the least likely scenario, requiring the Tories to win at least 326 seats in the 650-seat House of Commons.
Conservative leader David Cameron would form a government and he would be named prime minister.
2: The Conservatives form a minority government:
The Tories win both more votes and more seats than Labour but fall just short of a majority -- a situation that London School of Economics politics expert Patrick Dunleavy calls a "shallow hung parliament."
Because of the quirks of parliamentary arithmetic, if they win at least 310 seats they could form a minority government without turning to the Liberal Democrats, including by relying on the support of parties in Northern Ireland.
The Daily Telegraph reported Wednesday that the Democratic Unionist Party in the province has struck a pact with Cameron to give his party at least nine seats, in return for a list of demands.
3: The Conservatives do a deal with the Lib Dems:
Under Britain's skewed electoral system, the Conservatives could win the most votes but still finish behind Labour in terms of the number of seats won.
The average of polls on Thursday shows this is the current situation, with the Conservatives winning 35 percent of the votes but only 270 seats, while Labour still win 272 seats despite only taking 29 percent of votes.
With neither party able to take control of the hung parliament, there would then be a scramble for a deal and the Liberal Democrats would play kingmakers.
Tony Travers of the LSE said Labour would be more natural partners for the Lib Dems. "A Lib-Lab coalition would be very easy to set up, a Con-Lib would be very difficult," he said.
The Conservatives would probably have to make substantial moves towards offering the Lib Dems voting reform, which is not an idea the Tories currently back.
4: Labour clings on to power with Lib Dem help:
If Labour wins the most seats or the most votes but falls short of an overall majority, Prime Minister Gordon Brown would have the prerogative to try to form a government and keep the Labour party in power for a fourth term.
Lib Dem leader Nick Clegg has said he would consider negotiating with Labour, but only if Brown steps down as prime minister.
Speculation about a possible alternative leader has focused on Labour's current foreign secretary, David Miliband, or interior minister Alan Johnson.
Labour would probably have to offer the Lib Dems hope of reforming the electoral system by bringing in proportional representation, to secure their support.
© 2010 AFP