On 4 November, the world experienced a political earthquake. The aftershocks will be felt around the globe for years to come, including in Britain. All of us who experienced the moment will remember where we were when President-elect Barack Obama walked on to the stage at Chicago's Grant Park to address the world and to declare that "change has come to America". I always believed Obama could do it, but watching the moment unfold in reality was incredible.
That wonderful morning after, Londoners stopped me on the streets to celebrate.
But within hours I was brought crashing down to earth as David Cameron groped his way to making political capital from the historic triumph. We've come to expect that Cameron's Conservatives will seize any chance to detoxify their "brand". Yet even by their own standards, Cameron's message was patronising and opportunistic. In telling the President-elect that he was just "the first of a new generation of leaders", what he seemed really to be saying was: "This moment of history isn't about you and your achievement; really, it's all about me."
He wants to be Britain's candidate of change, claiming that Obama, like him, was a "novice". Such posturing distorts the truth about Obama's political apprenticeship. I know Obama. His political world-view is grounded in his experience as a community organiser. He has a deep-seated affinity with the people of Chicago's South Side among whom he has worked. He understands their daily struggles and the dreams they hold for their children. For Cameron to claim common cause with Obama is absurd and demeaning.
Cameron's political schooling was in a Westminster-centric world of special advisers, lobbyists and PR consultants. The truth is that "change" without context means nothing. The Conservatives cannot come close to the substantial body of political experience that underpins Obama's message of "change we can believe in". He won over voters because he had something to say about the economy, about protecting homeowners, supporting workers fearful of unemployment, and spreading opportunity in America. The "we" in Obama's promise of change is vital: his has been a message of people coming together to solve common problems. It is the essence of progressive politics.
It is no surprise, then, that in this time of unprecedented economic turbulence, Democrats are taking their lead from Gordon Brown. The Prime Minister has not only shown clarity and decisiveness in his response to the financial crisis here in Britain, but he has blazed a trail for other governments to follow. On housing, Obama's 90-day foreclosure plan mirrors Labour's measures to protect homeowners through new court protocols on repossession and "sale and rent back" schemes. And the PM's bold decision for the government to take stakes in the UK's leading banks is also being emulated by policymakers in the US.
Both Labour here and the Democrats in the US understand that globalisation cannot be stopped, but must be managed by governments acting in concert. Faced with economic instability, the Conservatives have no answer because their core belief is that good government is less government. They try to look wise after the event, but cannot deny that, at every stage, they have been calling for more deregulation. They have been wrong on Northern Rock, on short selling, and on City bonuses. The Conservative instinct is that good government is less government, that markets are best left to themselves and that other governments are not allies but potential problems.
With no answers to the economy, Cameron tells us "society is broken". Even the Mayor of London, Boris Johnson, has called this exaggerated claim "piffle". For all the challenges that the US faces, Obama does not argue that American "society is broken". His is a politics of hope, not a politics of pessimism; of re-engaging people, not talking the country down for partisan advantage.
So how does David Cameron propose to fix this so-called broken society? He says he will tackle poverty, but demonstrates that he has a get-out clause on doing anything about it, by telling us that "income redistribution and social programmes run by the state . . . have now run their course" and are "best achieved by Conservative means".
We in Labour do not believe in giving up on those causes and returning to the living nightmare of the 1980s, the poverty, the race riots and the soaring unemployment that I witnessed growing up in north London.
And neither does Barack Obama. He has condemned the "old and discredited" theory that giving "more and more to those with the most" means "that prosperity trickles down to everyone else". What it means, he said, is "you're on your own".
The Tory leader's claim that the "the state has failed" is simply wrong. Government cannot solve all our problems and nor should it try to. But those problems, whether of financial instability or social injustice, will not be solved without the state. Children must be given the education they deserve, security must be guaranteed, fair markets safeguarded and investment made for the future. Cameron and his party cannot back progressive ends if they do not will the progressive means to get there. The challenges of our time - managing global markets, eradicating poverty, improving life chances, and tackling climate change - require progressive solutions.
Fairness doesn't happen by chance: it depends on the choices that societies and their governments make. The Tories' mushy concept of "social responsibility" - that a "broken society" will somehow cure itself and a global economy regulate itself - offers no prospect of fairness or prosperity. And as Cameron tries to hijack the message of change we can believe in, the Tories' promises are exactly the opposite: unbelievable.
David Lammy is MP for Tottenham and minister of state for higher education