LONDON (AP) - Polls in Britain's razor-edge election opened early Thursday in a race that is likely to reshape the country's politics in historic ways.
Should Gordon Brown cling to power, his Labour Party will have pulled off one of the most unlikely political comebacks in modern times. Victory for the Conservatives' David Cameron would return his once-discredited party to office after 13 years.
More likely - in an election with important consequences for everything from the war in Afghanistan to the global economy - there will be no clear winner but an unprecedented boost for the Liberal Democrats and their leader Nick Clegg.
All three party leaders, accompanied by their wives, cast their ballots on Thursday morning. Earlier, Britain's tabloids had pulled the trigger with the Daily Mirror running a picture of Cameron along with the words, "Prime Minister? Really?"
The Sun, meanwhile, superimposed Cameron's face onto President Barack Obama's technicolor poster that read, "Hope." Only months ago, most thought the election would be the Conservatives' for the taking - but that was before the perfect political storm started brewing.
An embarrassing expense scandal last year enraged voters after lawmakers were caught being reimbursed for everything from imaginary mortgages to ornamental duck houses at country estates, bringing trust in British politics to a record low. And although lawmakers from all three parties were involved, the backlash was most severe for Britain's old guard, the Conservatives and Labour.
Labour's popularity, slipping since Tony Blair's landslide victory in 1997, took a nose-dive after the unpopular Brown took the reins. Then came the surprise success of Clegg, a 43-year-old who called for an overhaul of British politics during the country's first televised debates. His impressive performance thwarted Cameron and added to nagging worries over the extent to which the Tory leader actually overhauled the stodgy Conservatives.
The 43-year-old Cameron has also been hampered by his own elite background. Eton-educated and married to an aristocrat's daughter, many question whether he can relate to an electorate that has endured 1.3 million layoffs and tens of thousands of foreclosures over the past year and a half.
"This could go down as one of the most revolutionary elections in the history of this country," said Bill Jones, a political analyst at Liverpool Hope University. The stakes are high - both domestically and internationally.
As Europe grapples with Greece's financial crisis, global markets are waiting impatiently for Britain's election outcome - anxious to know how quickly work can begin to cut the country's record 153 billion-pound ($236 billion) deficit.
A Conservative majority would likely lead to a stock market rally and a boost for the British pound because the Tories favor more aggressive, and immediate, cuts than Labour to Britain's deficit. But even a Labour majority could see a rally because it would erase market uncertainty.
The impact of a hung Parliament - in which no party wins an absolute majority of the seats - is far less certain. Some analysts suggest fears about delayed action on the deficit could weigh on Britain's currency and stocks. Others say the markets have already factored that in and believe rapid action on the deficit is possible - as long as a new government is formed quickly.
If the Liberal Democrats are able to push through their main goal - overhauling Britain's centuries-old electoral system so it is more proportionate - the changes would favor center-left parties, and potentially shut Cameron's Conservatives out of power for decades.
"If David Cameron or Gordon Brown get into Number 10, nothing - nothing - will really change at all," Clegg said. Clegg and his wife Miriam Gonzalez Durantez - a Spanish citizen who is ineligible to vote in British general elections - posed for cameras after he cast his ballot in his constituency in Sheffield, northern England.
"I don't think my vote is a secret," he told reporters. Brown arrived with his wife Sarah to vote near his home north of Edinburgh, on Scotland's east coast. He said hello to reporters waiting outside the polling station, but made no comment. Cameron voted Thursday morning in his Oxfordshire constituency, accompanied by his wife Samantha. He told reporters, "I am feeling good. I will leave it at that."
This British election has already been historical. The country's first-ever television debates offered Clegg rare equal billing with Brown and Cameron, and he shined - combining his telegenic, friendly manner with sharp attacks on his rivals and the country's electoral system.
The Liberal Democrats - who have traditionally won about 20 percent of the vote since the party formed in a merger in 1988 - have held on to that unlikely surge although polls still put the Tories ahead but without a majority. The same system that Clegg wants to overhaul, in which the number of districts won - not the popular vote - determines who runs the country, could produce the most bizarre election scenario.
Labour could win fewer seats than the Conservatives, but still stay in power. That's because convention holds that in the event of a hung Parliament, Queen Elizabeth II should offer the sitting prime minister the first chance to try to form a government - even if his party wins fewer seats than the opposition.
In such a scenario, Clegg could find himself with the balance of power. The backing of his expected bloc of about 80 seats in a coalition would give Cameron or Brown the ability to form a government and pass laws. It's also possible that as early as Friday, Cameron will take the keys to London's No. 10 Downing Street after ousting the 59-year-old Brown - who may decide to quit if his party is humbled.
Even if Cameron defied predictions and won outright with a single-digit majority, it would be in stark contrast to Blair's landslide 1997 victory for Labour. Blair won a total of 418 seats, his party's largest number ever; a party needs 326 seats to command a parliamentary majority.
Several polls late Wednesday showed Britain on course for a hung Parliament. Without a firm mandate, the task for Britain's next leader of pushing through painful public spending cuts as well as a likely tax increase will be far more difficult.
"There's still a lot of head-scratching going around, and that might not change for weeks," says Steven Fielding, a political analyst from Nottingham University.