Opinion polls suggest the Scottish Nationalists will hold the balance of power after the next general election. What will this mean for the Union? Simon Wilson reports.
Why all the talk about the SNP?
The polling evidence suggests that the Scottish National Party (SNP) is very likely to be the third-biggest party in a House of Commons where no party has a majority after the general relection in May. This will potentially give it enormous bargaining power in its goal of an ever-looser union. What's more, the next parliament could very well be so "hung" that no two parties will be able to form a coalition that commands a majority.
If that happens, the next government will very likely be either a Tory or Labour minority administration and despite all the politicking of recent weeks (such as the Tories piling the pressure on Labour to rule out any kind of pact with the SNP as anti-British), the truth is that whoever leads the next UK government would need the support of Scottish MPs to get its programme through the Commons.
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How many MPs will the SNP have?
In the 2010 election, the SNP suffered from the first-past-the-post system, taking 20% of the vote in Scotland but only six of the 59 seats (the Tories came off even worse, with 17% of the vote and only one seat). The Lib Dems took 19% of the vote and a "fair" share of seats 11 while Labour took 42% of the vote and more than two-thirds of the seats (41).
This time round the SNP's post-referendum surge means that it is set to be the biggest party, and replace Labour as the dominant force that reaps the rewards of the UK's winner-takes-all system. Some recent polls even suggest it is heading for a virtual full house, taking up to 56 seats.
How probable is that?
The spread-betting markets are slightly more sceptical, with the consensus currently pointing to around 42 SNP MPs (and 283 Tories, 273 Labour, 26 Lib Dems and 7 Ukip). But that's still enough to suggest that Alex Salmond (pictured) will soon have the chance to make good on his resignation vow to "hold Westminster's feet to the fire on the vow' that they have made to devolve further meaningful power to Scotland".
What that will look like in practice is, like the election outcome itself, impossible to predict. But it is clear that under the UK's first-past-the-post system, there are several plausible but "unfair" outcomes on 7 May that have the potential to create lasting instability and to cause theties that bind the UK to unravel further.
Such as?
Most obviously, due to the fact that Tory constituencies are on average larger than Labour ones and their vote is spread more evenly, it is entirely plausible that the Tories will win the most votes on 7 May but Labour will win more seats, giving Ed Miliband first go at trying to form a government. Similarly, it is also perfectly possible that Ukip and the Greens win 20% or even 25% of the vote between them, but about 1% of the seats.
At the other extreme, the latest polling suggests the SNP looks set to win something in the order of 4% of the UK vote, but take 40 (or even 50) of the seats in Scotland.
Is a Labour-SNP coalition likely?
Part of the Tory electoral strategy will clearly be to focus English voters' minds on this prospect. Hence David Cameron's warnings this week about "an alliance between the people who want to bankrupt Britain and the people who want to break up Britain" and the launch of a poster campaign showing a tiny Ed Miliband in the pocket of a giant Alex Salmond.
But just as the Tories are warning that the SNP is set to let in Labour by the back door, the Scottish Labour stance is that a vote for the SNP will let in the Tories.
Both lines of attack, potentially, are valid, although there are plenty of other viewpoints. For example, an interesting piece by Conservative commentator Tim Montgomerie in The Times this week argued that a Tory-SNP deal is now the best way to secure English devolution and a stable transition to a federal UK. But both campaigns, in a sense, miss the main point.
So what is the main point?
That the 45% bloc that voted in favour of Scottish independence appears not just to be holding firm, but hardening. So Scots will vote SNP because they believe the party is best placed to defend Scottish interests, regardless of the make-up of the UK government. (Intriguingly, SNP voters tell pollsters that their preferred outcome of the UK election would be a Labour-SNP deal, but that their preferred prime minister would be David Cameron.)
A bloc of 40 or 50 Nationalist MPs might not in itself make another referendum more likely: the SNP is playing a long game, and has yet to decide whether to include such a vote in its manifesto for the 2016 Holyrood elections. But it would certainly ramp up the tensions that are pushing the UK either towards federalism or break-up (see below).
Will English voters say 'enough is enough'?
Whoever is prime minister after 7 May (and punters believethe most likely prime minister remains David Cameron), theprice for Alex Salmond's support most likely in a "confidenceand supply" deal, rather than a formal coalition wouldamount to home rule with full fiscal autonomy.
At that point,Scotland would be self-governing in everything exceptdefence and foreign policy, while England's laws would beskewed by a decisive bloc of MPs from north of the border. AsJanan Ganesh put it in the FT, "anyone who thinks the Englishwould wear this constitutional inequity for very long has readtoo many books about the nation's self-effacing stoicism".
