I bumped into Martin Bright as I was leaving the Sky News studios early on Friday morning after a grim election night. He asked if I would be interested in writing this article on what could be learned from the losses we had suffered.
The first lesson is: beware of New Statesman political editors approaching you in the early hours of the morning.
The second lesson is: don't make excuses. It was a grim night; don't spin the results.
But the third lesson is: fight back. I woke up on Saturday morning to a flood of text messages from friends, mostly non-political. They said two things: this is really depressing. And, please don't let this happen.
We should take hope from that second phrase. Please don't let this happen. That's not what people say when they have given up on your ideas. That's what they say when they're worried you're going to let the other lot in.
It's time to get off the floor, because our ideas are right. Just as we are being honest about this political setback, we need to be confident about our ideological position.
New Labour was born with a simple phrase: let's mean what we say and say what we mean. The Tories have learned exactly the opposite lesson. They have learned that they can't get elected by saying what they believe. So they say what we say, usually three years after we've said it, but hope that no one realises they don't mean it. They tell each audience what it wants to hear, no matter how contradictory.
But that kind of politics-as-marketing is on its last legs. People can see through politician-speak. They want an argument about ideas. They want politicians to say what they mean, even if that truth is hard to hear.
What is that truth? That globalisation is here to stay and increasingly affects us. When our mortgages dry up because of US lending or when our bread prices go up because of Chinese and Indian growth, globalisation has left the university seminar room and entered the British living room.
But underneath those fears about the credit crunch and the price shock is a deeper question: voters are asking how Britain will do in a global world. How will we compete, where will the jobs come from? The mood in the US shows the temptation of protectionism. The Conservative Party, stuck in the mindset of mid-20th-century national sovereignty, may be tempted, too. But it is a mistake. This is the core argument we need to win: that Britain is the kind of society that can prosper best from globalisation.
An open world calls for open societies. Open to the best ideas, a creative hub. Open to the best people, a magnet for talent. Open to new businesses, an entrepreneurial culture. Most of all, open to anyone to make the most of their potential.
How do we build such an open society? By investing in ideas, from science to the arts. By winning the positive argument for managed migration. By widening access to university. By ensuring that our schools stretch everyone, whatever their talent. And, it needs to be said, by ending child poverty.
We should take it as a compliment that the Tories are now having to pay lip-service to our ideas. They are now prepared to say they have been wrong on child poverty for at least two decades. Through gritted teeth, they admit that we were right.
This is a greater change than people have realised: the centre of political gravity has moved. Indeed, it has been moved by a decade of social-democratic government. The Tories have twice tried to win from the right and twice they have failed. So now, without changing much of the substance, they've polished the style and hinted at a move to the centre. That creates our opportunity: to point to the gap between what the Tories say they now believe and what their policies would do.
In David Cameron, we see the convergence of the worst trends in modern politics and the worst traits of traditional conservatism - an empty space filled for the moment with rhetoric. But if words ever have to be turned into deeds, then the conservatism will reassert itself. It is bound to, as his answers to straight questions make abundantly clear.
Campaigning against such a vacuous position is like shadow-boxing. But Cameron's tactical strength is his stra tegic weakness. His belief that government has no positive role is very well captured by his absent policies. The Conservatives have no policy for a reason. They think policies usually make things worse.
That's why Cameron has abandoned the fundamental role of government - making policy - at a time of global insecurity, when people most feel that they need the help of government. Of course, people want the freedom to get on, but they don't want to have to do so alone. They want a government that does everything it can to lift the barriers in their way, not a government that just gets out of the way.
Take the debate on child poverty. Labour wants to end child poverty, not just because this is right, but because no child can have a fair chance if he or she grows up in a poor family. The Tories know they can't be against this. But what motivates them to talk about social injustice today is a desire not to lift children out of poverty, but to lift people's perceptions of the Con servative brand. They want to sound as if they're against child poverty, rather than have policies they would actually have to fund if they won.
And the result? On 1 May, it became clear that they would like to water down the goal, so that 2.5 million children would no longer be defined as poor. That's the difference between lip-service and policy: the lives of hundreds of thousands of children. We've lifted the equivalent of 20,000 classrooms of children out of poverty. In contrast, if Tory policies had continued after 1997, 1.7 million more children would now be in poverty. Britain is on its way to becoming a different, fairer society. If the Tories won the next election, the journey would at least stall, and likely reverse.
It is in that gap between words and policy that we should make our stand. If there is a positive to come out of the past fortnight it is this: the fight is on. Every day, from now until the gen eral election, we must contrast our vision of Britain's future with the absence of a new vision from the Conservatives.
The Tories' claim to be ready for government comes at a price - greater scrutiny. Local elections, unfortunately, can be a referendum on governments. General elections are a choice. Cameron will now find that while following public opinion is easy, leading takes real vision. They will struggle in the spotlight.
James Purnell is Secretary of State for Work and Pensions and Labour MP for Stalybridge and Hyde