From now until September 18th, the Scottish referendum will rightly dominate national politics. Tuesday night’s debate between Alistair Darling and Alex Salmond is the Yes campaign’s last and best chance to gather the momentum it needs to pull off an improbable victory.

But, as British Election Survey data shows, the result of the referendum is not a foregone conclusion. If the ‘undecideds’ keep breaking the same way, the result will be No 53.6 per cent, Yes 44.6 per cent. This is too close for comfort.

But if Scotland votes No, attention will quickly shift to next May’s UK election. It is a sign of how speeded-up our politics has become that David Cameron’s political career could be over two years before his 50th birthday. But, as I say in the magazine this week, the next election remains winnable for him, particularly if winning is simply defined as him remaining prime minister. If Cameron is to do this with the constituency boundaries against him, the left unified and the right divided, he can’t afford any slip-ups. He will have to get everything right.

Tags: 2015 general election, Alex Salmond, David Cameron, Scottish independence referendum