The Scottish independence referendum will decide David Cameron’s place in history

David Cameron was right to let the Scottish people vote on their future and may even reap some reward for it. It is always a risk, democracy. But now it seems to be paying off for him. Considering that Ukip was supposed to have split the Conservative vote, the Tories did well in the local and European elections, with a share of the vote just one and a half percentage points less than Labour’s. This week, the Tories might even hold Newark in the by-election. A Survation poll in the constituency put them eight points ahead of Ukip with eight days to go. It could be the first seat held in a by-election by the Conservatives in government since William Hague in Richmond in 1989.

The next electoral challenge, though, is the big one. The Scottish referendum in September. This is possibly the most important event of Cameron’s time as Prime Minister. The official campaign, during which spending limits apply, started on Friday. All politicians say that there is no room for complacency. This invites the question: why does complacency take up so much space? You might have thought that neurotic anxiety about imminent defeat would need a clear area for pacing up and down. Still, I am not a politician, and my complacency is quite compact: I think Scotland will vote to stay in the United Kingdom.

If so, that would be a great vindication for Cameron. He will be recognised as an astute judge of high politics, which he hasn’t always been. This is not the place to list all his errors, but he got the initial response to the banking crisis wrong; he allowed Nick Clegg to sabotage the boundary changes that would have equalised constituencies; and he cut the top rate of income tax, fatally undermining the Government’s “all in it together” rhetoric.

But if Scotland votes to stay in the UK, all that will fade a little against the brilliance of his triumph. His assessment that he could not be seen to stand in the way of the Scottish people will, after the event, be regarded as obviously right. I do not see how any prime minister could have refused to allow the referendum to take place, but a different one might have tried to delay it or to impose conditions. Cameron seems to me – although what do I know? I’m Scottish but I don’t live in Scotland – to have handled it exactly right. His tone has been respectful, statesmanlike and reasonable.

Some of his subsidiary decisions have been controversial. He refused to take part in the stunt of a TV confrontation with Alex Salmond, leaving it for Scots to debate with each other, while making it quite clear that he – like most people in the rest of the UK – doesn’t want them to go. He banned government departments from engaging in contingency planning for Scottish separation. This upset Professor Peter Hennessy, who told the House of Lords he thought it infringed the duty of the Civil Service to prepare for all eventualities. But it would have felt like defeatism, and that decision too would be vindicated by success.

Cameron has not been tempted for a moment by the short-sighted calculation of Tory party advantage – nor could he possibly be. No prime minister, and certainly no Conservative prime minister, could preside calmly over the break-up of the UK. In any case, the idea that the Tories would win elections for ever in a Scotland-free UK is a fallacy. Labour under Tony Blair won a majority of seats in England, including in 2005.

So winning the referendum would give Cameron some lustre. Not as much as he might deserve. Many English, Welsh, and Northern Irish people might look up briefly from their iPads and record momentary satisfaction that they are not being asked to live in a different country. They are hardly going to hang out a Union flag and acclaim Cameron as the leader for whom the nation has been searching since the dark days of the Blitz, but it will shift something in his favour.

Keeping the country united is a negative achievement, yet it is the sort of thing that historians will recognise. Until this year, Cameron’s one-line entry in the list of prime ministers and their achievements was looking a bit tentative: “Started to balance the books.” In September, it will look more substantial.

This will also have an effect on Cameron’s manifesto for the general election. A successful referendum in Scotland would make the promise of a referendum on EU membership look more like respecting democracy and less like a desperate ploy to keep his party united. The timing of Cameron’s referendum is not ideal, and the changes he seeks are mostly cosmetic, but Labour has a big problem trying to argue with the principle.

We are getting ahead of ourselves, though. There is a general election first. However, if Cameron wins the Scottish referendum, he will be in a stronger position to win next May.

Twitter: @JohnRentoul