Peter Duncan is Managing Director of Message Matters, and is a former MP and Chairman of the Scottish Conservatives.

Insanity. Doing the same thing over and over again and expecting different results.

Einstein would have had great fun examining Conservative strategy on Scotland over the past 40 years. Ever since Margaret Thatcher reversed established Conservative thinking and confirmed opposition to devolution, Conservatives have been on the back foot here. Yet her legacy in Scotland is, despite the rhetoric of many, overwhelmingly positive in transforming a nation that built useless cars, extracted expensive coal and manufactured uncompetitive steel and ships, into an economy where bio-medical research, world beating IT and computer gaming is now the foundation of an economy transformed since the 1970s.

However, her about-face on devolution was an uncharacteristic and extremely damaging misjudgement.

It put in place a plan for Scotland that has broadly endured to this day. Contain and bear the losses of seats. Belatedly pledge small steps on local determination, when large leaps were required. Hope for the best. And, er, that’s it.

I hoped for a genuine change of direction when, after securing a relatively narrow win in the independence referendum, The Prime Minister proclaimed on the steps of Number 10 that we were heading for a fundamental reassessment of our country’s constitution. On reflection, it was a speech that could be read in two ways – either setting a path for a new localist strategy, passporting real devolved power to the nations and regions of the UK; or, alternatively, just that the Government was determined to deliver English votes for English laws. Support for the latter is right, but the former would have been so much more powerful.

As a result, the same old tired strategy has been maintained. Devolve what we are forced to, not what is right. Transfer the minimum of powers when we are backed into a corner, not as a result of true conviction that our country is far too centralised.

There have been admirable expressions of support for “our United Kingdom” from Conservative Party leaders for many years, but short-term political advantage is usually the enemy of long-lasting good relationships within the union. There is no better example than the established 2015 Conservative strategy of playing the SNP card to win over middle England. Short-term perceived gain which will incur long-term guaranteed pain.

As the polls have remained disappointingly close, the frightening prospect of a large Scottish Nationalist contingent at Westminster after the election is being used to clobber a weak Labour leadership. Playing up Nicola Sturgeon has been seen as a device to undermine Ed Miliband. It has been a tempting game to play – my enemy’s enemy is my friend – but is ill-judged, and is playing with fire.

Much has changed since September 14th last year. Despite the wishes of most inside the Westminster village, Scotland has not disappeared off the landscape for a political generation. A referendum result that was closer than it should have been has lead directly to a momentum shift towards the SNP that is unprecedented, and is rapidly becoming entrenched.

It has been a tempting tidal wave for Conservative strategists to ride. After all, Sturgeon gains are Miliband losses, in the main, and the coffee shop chatter is all of Labour losing a decisive tranche of 40 seats that will keep the baton in David Cameron’s hand when it comes to delivering a Queen’s Speech. However, the 2015 Conservative narrative is exactly what the SNP would have chosen. Target voters in those new Scottish marginal constituencies love the thought of Alex Salmond with Ed Miliband in his pocket – time and again, the desired election outcome in Scotland is a Labour Prime Minister being manipulated by the SNP.

My message to those strategists is “be careful what you wish for”. A nationalist contingent of 40-50 MPs will make for a very different Parliament, and not in a good way. And that kind of number will play a key part in laying foundations for another independence referendum.

We need to be clear: there remain only two endgames for the Scotland “issue”. Either an independent nation is created at the second time of asking, or we establish a new federal basis for the United Kingdom. The sooner Conservatives accept that reality, the greater the chance of avoiding outright independence.

Usefully, what has become inevitable also has the benefit of being right. Conservatism finds its surest roots in localism, and now would be a good time to let those roots grow.

Of course, the naysayers will bleat that this kind of constitutional change just can’t be done, isn’t very British and won’t work. We’ve become cosily comfortable over the years with a centralised state – the business of government loves the sense of control that centralisation provides. We need to learn to let go.

However, the City Deal model provide us with something substantial on which to build. Local determination, local decisions and local accountability. In the long run, I’ll wager that a new sense of local accountability will be a good thing for Conservative prospects. Genuine accountability for taking the tough decisions necessary to govern sustainably are usually good news for the centre-right.

So whilst contemplating the coming four weeks, and the potentially decisive impact of the 2015 Scottish Nationalist cohort of MPs, spare a moment for the challenge we’ll be set by the Scottish problem of 2015. Another rising tide of nationalist sentiment – are Conservatives willing to seize the initiative, or remain despairing observers of the “Scotland problem”?

Federalism is now the future. A country built on localist foundations, where decisions are taken centrally when they need to be, and local democracies in charge when they don’t. It’s a vision that can inspire a northern powerhouse, keep London driving forward, and retain Scotland within the UK.

For lovers of our united Kingdom, the options are now clear – federal or bust.