The Scottish Independence debate for Thursday’s referendum on separation from the U.K. has escalated as both sides are scrambling to woo undecided voters. More than 4.2 million Scots are registered to vote on whether a political union that has stood since 1707 will come to an end, but it’s the 500,000 undecided voters that hold the key to the decision.

Those opposed to Scottish independence argue that the country’s economy may be sent into a tailspin, and those in favor accuse ‘No’ voters of scaremongering.

In a last-ditch effort to influence voters, British Prime Minister David Cameron, Labour Party Leader Ed Miliband and Liberal Democrat chief/Deputy Prime Minister Nick Clegg all signed a pledge in the Daily Record vowing to deliver “faster, safer and better change” for Scotland with increased powers and a fair share of resources should the country vote “No”. The joint letter pledges that the U.K. will “ensure opportunity and security for all by sharing our resources equitably across all four nations.”

But Scottish National Party leader Alex Salmond pointed out that the promises were vague, reminded the government’s record on delivering pledges and dismissed the so-called “vow” as a “last minute desperate offer of nothing.”

On the other side, Labour Party politician Douglas Alexander was worried about the “risks, uncertainties and costs” of a “Yes” vote. “With just 48 hours to go, they can’t even tell us what currency we’ll be using,” he said.

Meanwhile, the countdown is on for the September 18 referendum with the latest polls too close to call. Both sides are passionate, but it seems that the balance of power will be held by the “don’t knows”, a group of undecided voters that may be as few as 500,000.

Betfair has already reached a foregone conclusion

Even though the polls say that the outcome of the vote is too close to call, Betfair is already paying out more than 100,000 pounds to customers backing a “No” vote.

Here’s what the U.K. will look like without Scotland