ONE word dominates Election Day 2015. Not victory, relief or anticipation – but uncertainty. Even bookies with a better track record on election results than academics or pundits have decided not to narrow the odds.

Either Labour or the Tories could squeeze home as the largest single party or clinch an overall majority, but more likely the “winner” will be proclaimed once a deal’s been done – or not done – with smaller parties like the Lib Dems and SNP. No wonder panicked political leaders are looking beyond today’s vote and tonight’s result to tomorrow’s guddle. The will of the people – expressed through the broken mirror of first-past-the post voting – seems to be as clear as mud.

Yet the modern voting public is no stranger to uncertainty – encountered first at the 2010 General Election when Labour’s unwillingness to negotiate with the Lib Dems pushed them into coalition with the Tories; and more recently on September 18 when four million Scots narrowly voted to remain within the UK.

On each occasion scaremongers predicted mayhem following the vote – on neither occasion did mayhem actually occur.

But now that the party of the Establishment could finally receive its jotters, things are looking different. This time, we are told, uncertainty could breed something infinitely more dangerous – a lack of legitimacy for the next British government

Look around – the L-word is everywhere.

David Cameron said on Tuesday: “There’s a massive credibility problem with this idea that you can have a Labour government, backed by the SNP, only fighting for part of the country.” And what credibility problem would that be for voters outside the Tory shires? Nobody really spells it out – but they don’t have to. The nameless fear of undefined chaos is the stock in trade of Project Fear.

The Daily Telegraph obligingly echoes the message: “The next government needs to have legitimacy” with a headline “Nightmare on Downing Street”, referring to John Major’s warning that a Lab-SNP deal could “tear the nation apart.”

Meanwhile the UK edition of the Sun calls on voters to “save Britain’s bacon from the chaos of a Labour government propped up by Nicola Sturgeon’s SNP” and a Guardian video by John Harris in the marginal seat of Nuneaton features a massive billboard portraying Alex Salmond in burglar’s black polo shirt pickpocketing an innocent passer-by. The strapline reads: “Don’t let the SNP grab your cash.” Local opinion has it that “if the SNP gets in, we’re done for.”

Even the Independent joins in with “fears of a legitimacy crisis for the next government” after a survey shows 70 per cent of (presumably English) voters think the SNP shouldn’t be able to veto UK Government policies unless they affect Scotland.

In short, English voters are being primed to overreact hysterically should Labour try to form a minority government on Friday –whether it’s a formal deal that includes the SNP, discreet dialogue or semaphore signals at dusk.

Will this obvious attempt at mood-fixing work – or are most voters south of the Border sensible enough to see that “messy” outcomes are the fault of the system and the uninspiring choice between four lacklustre parties south of the Border – not the Scots.

It’s the antiquated Westminster system, in which only a third of voters choose each government, that’s hopelessly illegitimate. That problem could have been sorted decades ago by introducing proportional representation, abolishing the House of Lords, returning more cash and decision-making power to communities and establishing a systematic form of federal government across the whole of the UK (including England). But neither main party has ever really fancied such dramatic constitutional change for England. The hope was that “seeing off” the Scots would save the rest of the UK from having to modernise itself.

But the darned Scots are back and now Labour is caught betwixt and between – trying to stop the Tories from poisoning the well of public opinion against a deal but treating the Nats like political untouchables at the same time.

Perhaps that’s why Nicola Sturgeon has weighed in on legitimacy too.

She said: “The test of legitimacy that must be applied to whatever Westminster government is formed cannot simply be that it is the largest party in England. The test … is whether a government can build a majority and command support that reflects the whole of the UK.”

You can see where the SNP leader is going with this. It would be a mockery of democracy if Scots vote SNP in historic proportions only to see a Labour or Tory government lock them out of influence at Westminster. And yet, you can see the objection too.

A government that reflected the whole UK would require SNP-dominated Scotland to work with the Tory-dominated south-east of England and Unionist-dominated Northern Ireland. No one’s suggesting that. But a new poll for the Electoral Reform Society shows 54 per cent of voters back power-sharing of some kind if a second election in 2015 is the alternative. So change and compromise is in the air – amongst voters at least.

Now it’s up to the politicians.

Change is in the air – at last.