Britain's dead-heat election

The results of exit polls are projected on to the side of Broadcasting House, the headquarters of the BBC, after voting closed in Britain's general election, in central London, May 8, 2015. REUTERS/Eddie Keogh

Supporters of the Scottish National Party celebrate results at a counting centre in Glasgow, Scotland, Britain May 8, 2015. REUTERS/Russell Cheyne

Supporters of the Scottish National Party celebrate results at a counting centre in Glasgow, Scotland, May 8, 2015. REUTERS/Russell Cheyne

Britain's Prime Minister David Cameron greets supporters as he arrives at the counting centre for his local constituency as ballots are tallied in Britain's general election in Witney, May 8, 2015. REUTERS/Toby Melville

Alex Salmond, the former Scottish National Party who is now running for Parliament, speaks to television journalists at a counting centre in Aberdeen, Scotland, May 8, 2015. REUTERS/Cathal McNaughton

United Kingdom Independence Party MP Douglas Carswell arrives at the counting centre where he is fighting to keep his seat in Britain's general election, in Clacton, May 8, 2015. REUTERS/Neil Hall

An electoral worker empties a ballot box after polls closed in Britain's general election at a counting centre in Doncaster, May 7, 2015. REUTERS/Darren Staples

An electoral worker counts ballots as polls close in Britain's general election, at a counting centre in Sheffiled, May 7, 2015. REUTERS/Andrew Yates

A ballot is held up for count staff to check at Winter Gardens after polls closed in Britain's general election, in Margate, southeast England, May 7, 2015. REUTERS/Suzanne Plunkett

Ballots are counted for South Thanet at Winter Gardens after polls closed in Britain's general election, in Margate, southeast England, May 7, 2015. REUTERS/Suzanne Plunkett

An electoral worker empties a ballot box after polls closed in Britain's general election at a counting centre in Glasgow, Scotland, May 7, 2015. REUTERS/Russell Cheyne

An electoral worker with a Scottish Saltire painted on her finger nails counts ballots after polls closed in Britain's general election at a counting centre in Aberdeen, Scotland, May 7, 2015. REUTERS/Cathal McNaughton

Polling station workers place signs outside a polling station in Islington, in London, Britain, May 7, 2015. REUTERS/Peter Nicholls

Prime Minister David Cameron and his wife Samantha leave after voting in Spelsbury, central England, Britain May 7, 2015. REUTERS/Toby Melville

Labour Party leader Ed Miliband arrives to vote with his wife Justine in Doncaster, northern England, Britain, May 7, 2015. REUTERS/Darren Staples

A man works out on a punch bag in East Hull Boxing Club as people arrive to cast their votes in Hull, Britain May 7, 2015. REUTERS/Darren Staples

An advertising van with images of David Cameron and Ed Miliband drives around Parliament Square, central London, Britain, May 7, 2015. REUTERS/Phil Noble

Nigel Farage, leader of the United Kingdom Independence Party (UKIP), leaves after voting at his polling station in Ramsgate, southeast England, May 7, 2015. REUTERS/Suzanne Plunkett

Liberal Democrat leader Nick Clegg arrives to vote with his wife Miriam Gonzalez Durantez at a polling station in Sheffield, Britain, May 7, 2015. REUTERS/Andrew Yates

Nicola Sturgeon, the leader of the Scottish National Party, waves as she stands with her husband Peter Murrell after voting in Broomhouse, Scotland, Britain, May 7, 2015. REUTERS/Russell Cheyne

Chelsea pensioners walk to cast their vote in London, Britain, May 7, 2015. REUTERS/Paul Hackett

A dog stands outside a polling station in central London, Britain May 7, 2015. REUTERS/Stefan Wermuth

Protesters hold up placards and a banner as David Cameron and his wife Samantha leave a polling station after voting in Spelsbury, central England, Britain, May 7, 2015. REUTERS/Eddie Keogh

Ed Miliband leaves after voting with his wife Justine in Doncaster, northern England, Britain, May 7, 2015. REUTERS/Darren Staples

Scottish Labour Party leader Jim Murphy gestures as he arrives to cast his vote in Glasgow, Scotland, Britain, May 7, 2015. REUTERS/Russell Cheyne

Scotland's former First Minister, Alex Salmond (2nd R), arrives with supporters at a polling station in Ellon, Scotland, Britain May 7, 2015. REUTERS/Cathal McNaughton

Chelsea pensioners walk to cast their vote in London, Britain, May 7, 2015. REUTERS/Paul Hackett

Nigel Farage gestures as he arrives to vote at his polling station in Ramsgate, southeast England, May 7, 2015. REUTERS/Suzanne Plunkett

Poll clerks are seen in a public launderette being used as a polling station in Oxford, Britain May 7, 2015. REUTERS/Eddie Keogh

The Big Ben clocktower and the Houses of Parliament are seen in the early morning in central London, Britain May 7, 2015. REUTERS/Stefan Wermuth