Election 2015: Never before has Scottish politics had such a huge potential impact on the outcome of a General Election

THE astonishing opinion poll finding that the Scottish Nationalists could win every single seat in Scotland today has shaken both the Tories and Labour to their very foundations. They are quaking in their boots.

SNP leader Nicola Sturgeon speaks to party activists outside the National Galleries of Scotland in Edinburgh on the last day of the General Election campaign. (PA Wire)

Never before has Scottish politics had such a huge potential impact on the outcome of a General Election nationwide. This time they are absolutely dominating it.

Even if the outcome in the early hours of tomorrow contradicts the findings of this poll, and other parties manage to scrape home in one or two seats north of the border, it is still a massive blow to the conventional parties.

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And if the poll is correct, how can anyone deny the right of the Scots to hold another breakaway referendum - and this time probably win it?

Just as alarming: how could, in these circumstances, Ed Miliband refuse any kind of arrangement to do a deal with the SNP, despite his firm words to the contrary, if Labour emerges the largest party in a hung Parliament?

And in the event of such a situation, it could mean that Nicola Sturgeon’s threat to “lock out” the Tories would materialise.

Among those who have always opposed Scottish independence are Tony Blair and Gordon Brown. So why on earth did they enable the SNP to progress halfway to their goal by having the Parliament set up in Edinburgh in the first place?

A heavy price is now being paid for this colossal and stupid blunder.

WAS the Prime Minister being commendably bold or simply downright reckless in his pledge that if the Conservatives win the general election, there will be legislation to guarantee no rises in income tax rates, VAT or National Insurance until 2020?

The thing is, David Cameron, whatever else he is, is not a clairvoyant. It is a huge gamble for a politician at his, or indeed at any level, to give such an all-embracing undertaking when he cannot have a clue what the economy will do over the next five years.

You can hardly blame his political enemies for describing it as “a desperate, last-minute gimmick”, a promise which he may be forced to break if circumstances arise beyond his control.

On the face of it, his announcement appeared straightforward with nothing sinister to read between the lines, which would allow him to escape from this solemn obligation. Mind you when (or rather if) the legislation comes before Parliament, it may well include some very obscure clauses which would enable him to “get out of jail” honourably.

But this pledge will not be forgotten by his opponents. If - assuming Mr Cameron remains in Downing Street - he does have to renege on it, there would be an almighty row - and Cameron could become politically damaged goods for ever. It certainly looks like a pledge too far.

ED Miliband was taking a huge gamble when he agreed to be interviewed by Russell Brand. If his objective was to “connect” with the “yoof” vote (such as it is), it was probably a gamble worth taking.

The Labour leader must have been aware that this action would give rise to withering attacks from his political enemies. But, it seems, he was prepared to live with that - he even might rather have relished it.

But, in my view, there was one very good reason why Miliband should not have gone anywhere near Brand.

It was this: just a few days ago, Brand delivered an astonishing verbal attack on Ed Balls, the shadow Chancellor, denouncing him using strong language.

Purely out of distaste for this and, more importantly, as an act of loyalty to his right-hand man, Miliband should have told Russell Brand where to put his interview and subsequent endorsement.

Chris Moncrieff is a former political editor of the Press Association.