What if an SNP deal with Labour at Westminster spelled the end for independence?

The blinding sunlight is that of a new dawn breaking over the UK, and the hysterical chatter comes from a Downing Street press corps desperate to see who will be coming and going now that neither of the main parties has won a clear majority. That faint rumble hailing from the west? Coachloads of SNP MPs making their way from Heathrow for a victory photograph outside the Commons. Cheerio Blair's Babes (and good riddance), hello Nic's Nats. Back in Scotland, the party's supporters, many of them so new they still have the labels attached, celebrate into the weekend.

Scenarios, scenarios. Given how well the campaign is going for the SNP, its supporters could be forgiven for simply enjoying these days and not thinking too far ahead to stickier times. Cannier heads should prevail, though. Come May 8, the SNP might be standing on a travelling walkway towards independence. Or it could have wandered into quicksand.

One could quote from any number of political thinkers through the ages on the importance of planning ahead in politics. Instead, since it is Friday and we are kicking back for the weekend, let us turn instead to a more left-field political philosopher, this one by the name of Tony Soprano. It was once said of New Jersey's leading waste management consultant, a man with a soft spot for the Chinese military strategist Sun Tzu if ever there was one, that the reason he was so successful was because he could think not just two or three steps ahead, but 20. Thus far, Nicola Sturgeon, Scotland's First Minister, has shown herself equally adept at this endeavour (that's thinking ahead, not waste management consultancy). No-one desiring a political career joins the SNP in the mid 1980s if they cannot game plan to gold standard.

One party that has certainly been strategising, if only on the hoof, is the Tories. To deflect attention away from the failure of their campaign to land a decent punch on Labour, they have taken to goading English and Scottish nationalism. The last refuge of the scoundrel indeed. Today, as a further sign that the party does not see us as all in this together, never mind better together, the Conservatives will publish a separate manifesto for England in which much talk is expected of English votes for English laws, impact statements, and several more ideas recently liberated from the back of a fag packet. It has become commonplace in Scotland to ridicule such obvious and divisive tactics from the Tories, to imagine that little of the mud being slung will stick. But in a YouGov poll for The Sun this week, 58 per cent of respondents thought the SNP holding the balance of power in Scotland would be a bad thing. Interestingly, the split among Scottish participants was 45 per cent good, 44 per cent bad. All this is with two long weeks to go. Even given all the usual health warnings about polls, single ones especially, this ought to worry the supporters of an independent Scotland. If such a trend continues, and the Tories step up Project Fear: Mark Two, the atmosphere in England could be bordering on fraught come May 8.

From here, there are two ways in which the SNP holding power with Labour could pan out. The first scenario is the one that doomsayers, led by the Tories but not made up of them exclusively, favour. This has SNP MPs behaving like a cloud of midges/elected representatives of the people (delete where applicable), making a regular nuisance of themselves/exercising their democratic rights, on a vote-by-vote basis. A red line comes up, the Labour Government falls, even with the safeguards in the Fixed-term Parliaments Act, and it is 1979 all over again.

In Scotland, the pro-independence movement indulges in a mass "told you so", arguing that even with substantial representation at Westminster, the Union simply does not work for Scotland. The UK electorate, meanwhile, does its duty again. This time Project Fear: Mark Three is more effective and fewer SNPs are elected. But it does not matter because the point has been proven - Westminster is bust, here we come Holyrood 2016, and another independence referendum.

While this might seem like a win-win situation to some, it would hardly be a positive basis on which to fight any future Yes campaign. An independent Scotland, if it resulted at all, would start life in an atmosphere of rancour. Alternatively, failure at Westminster - because that is ultimately how it would be seen outside the Yes camp - could deepen division in Scotland and make a No vote more likely.

Now we come to the second scenario. If our Mr Soprano was of the Yes persuasion, this is the one that ought to have him tossing and turning at night. In this set-up, an Ed Miliband-led Labour Party proves itself to be as nakedly greedy for power as every other outfit and does a deal with the SNP, formal or informal. There is an initial skirmish over red lines, but there is nothing that cannot be kicked into the long grass (yes, even Trident). The SNP settle into their role as the Labour Government's conscience, putting the brake on austerity gently but firmly. In time, things settle into a smooth enough groove. The electorate in Scotland approves of the way the SNP is doing the business in Westminster, approves so much that they want to keep the status quo - a parliament at Holyrood, and efficient and effective representation at Westminster. Rock the boat with independence? Do their heads look as though they button up the back? And so independence withers on the vine.

It would be a funny old world indeed if success on May 7 was a turning point for the independence cause, but not one of its choosing. And who is to say which direction is best? The SNP is the fastest growing political movement in Britain. The enthusiasm of its members is obvious, their ultimate aim clear. But there is no guarantee that all will agree on the best way to achieve it.

There is one more possible outcome, this one we shall call the William Goldman scenario after the double Academy Award-winning writer who wisely declared that "nobody knows anything". This argument holds that the big mo towards independence is ultimately unstoppable; that the SNP, from winning a majority at Holyrood to securing more than 50 seats in Scotland, have a knack of confounding predictions of political strategists; and that it will all be all right on the night of May 7, and for enough time thereafter to close the gap between Yes and No in any future referendum.

Scenarios, scenarios everywhere and not a certainty to be had. Plan 20 moves ahead? Better make that 40.