London - There's only one good bet in Britain's razor-edge election: It's 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, and a good showing for Liberal Democrat upstart Nick Clegg.

Only months ago, most thought the election would be the Conservatives' for the taking - but that was before the perfect political storm emerged.

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, an affable 43-year-old who called for a complete overhaul of British politics during the country's first-ever televised election debates. His impressive performance thwarted Cameron and added to nagging worries over the extent to which the Tory leader has 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 $236 billion deficit, and whether the parties will be able to cooperate to pass key legislation.

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 huge budget deficit. But even a Labour majority could see a rally purely because it would erase market uncertainty.

The impact of a hung Parliament - in which no party wins enough seats to govern outright - is far less certain.

Some analysts suggest that 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.

Britain's four-week electoral campaign was transformed by the country's first televised debates. The three prime-time clashes 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, despite a dip in the last week of the campaign.

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 perhaps 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.

However, Clegg has already indicated his price will likely be Brown's resignation, as well as key government positions and a commitment to a proportional voting system - which Cameron bitterly opposes.

Graham Smith, of Republic, a lobby group seeking to abolish Britain's monarchy, said the queen could face a public backlash. "The queen is terrified of making a decision because of the consequences for her if that decision is unpopular," he said.

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.

Polls late Wednesday showed Britain on course for a hung Parliament.

A survey by Populus for the Times of London put support for the Conservatives at 37 percent, with Labour getting 28 percent and the Liberal Democrats 27 percent. The Times calculated that would give the Conservatives a total of 301 seats in Parliament - 25 short of a majority.

No margin of error was given for the poll of 2,505 adults carried out Tuesday and Wednesday. However, surveys of that size typically have a margin of error of plus or minus two percentage points.

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.

"People are shocked that something like this is happening in Britain," says Steven Fielding, a political analyst from Nottingham University. "This election is really uncharted territories. There's still a lot of head-scratching going around, and that might not change for weeks."

Whichever candidate becomes Britain's next leader, his debut on the world stage will come June 25, as the Group of Eight nations gather in Canada for a summit.

By then, Britain's ties to its allies may have changed. Though all three parties support the Afghanistan campaign, both Cameron and Clegg hint at looser links to the United States.

On London's stance toward Washington, Cameron has said: "We don't overstate it and don't ever think that it's a sort of equal partnership because it isn't." His party's manifesto vows to build a new "special relationship" with India and bolster relations to other neglected partners.