It already seems so long ago, when, like you, we anxious eco-Brits spent a tense few minutes on Jan. 20 deconstructing Obama’s inauguration speech.

There was plenty to cheer: “The ways we use energy strengthen our adversaries and threaten our planet.” (Well spotted!) “Without a watchful eye, the market can spin out of control.” (Bloody good point!) “We will restore science to its rightful place.” (Yes! Stuff the creationist nutters!) “The success of our economy always depended not just on the size of our Gross Domestic Product, but on the reach of our prosperity; on our ability to extend opportunity to every willing heart.” (Ooh! A coded death knell for growth-driven economics!)

And some food for thought: “Our goods and services no less needed than they were last week or last month or last year.” (Hmm. Not much then in the case of GM, Ford, et al?) “We will build the roads and bridges, the electric grids and digital lines that feed our commerce and bind us together.” (Not much poetry in suburban light-rail systems, I guess, but can you at least do the roads last?) “We will harness the sun and the winds and the soil to fuel our cars” (and trains!). “We will not apologize for our way of life.” (That’s fine, but don’t let it happen again!)

By the end, our mood was rather chipper. Swept along by the euphoria, we felt the difference in ourselves. Even those who remembered the morning of May 2, 1997, when Tony Blair surfed a similar wave into power in the U.K. — and the disappointment that seeped in over the ensuing years as he turned into Dubya’s best mate and a safe pair of hands for the same old elites — couldn’t quite keep the spring out of our step.

Three weeks on, some observers here have already decided the honeymoon — if there ever was one — is over, and President Barack Obama, up to his neck in the proverbial, is going to need an awful lot of substance to go with his undeniable style if he is to avoid becoming America’s Tony Blair.

There’s some delight at this parallel amongst right-wing commentators here. One of their number, James Delingpole, a sort of Brit P.J. O’Rourke-lite, is in the U.S. right now promoting his book Welcome to Obamaland: I Have Seen Your Future and It Doesn’t Work, in which he paints Obama as a sort of crypto lefty green analogous to Blair. Trailing this work in the Spectator, he says Obama “may be a fantastic guy, and look great, but he will bring a ragbag of scuzzballs, communists and eco-loons to power with him,” and by falling for Gore’s “grotesquely misinformed claptrap President Obama will be costing the hard-pressed U.S. economy billions of dollars for schemes that will hamstring American heavy industry.” That claptrap is An Inconvenient Truth, by the way.

Leaving aside the rather astonishing thought that Blair was some sort of radical, green or red, or that Obama could be worse for the U.S. than was Bush, the 137 comments on Delingpole’s piece show that, while you don’t have to be a climate-change denier to hate Obama, it’s one of many reasons why some are happy to write him off as a malevolent snake oil salesman intent on the ruin of America and the rest of the free world.

All this might make you think doing the green thing can only get harder for politicians in a recession. When, even in the good times, the pursuit of sustainability was limited to what could be sold to the public as good news or an attractive lifestyle, surely it must be even more curtailed in the downturn? And if it’s hard for politicians, how much harder will it be for consumer-facing businesses, at the sharp end of our tendency to say one thing and buy another?

We’re so used to politicians and businesses stoking and tracking our fickle appetites, it’s hard to imagine things could be different. But in this sense, at least, the Blair/Obama analogy fails. While pre-Iraq Blair was the perfect PM for the good times — making sure that everyone could feel comfortable, even self-righteous, about rising debt, political indifference, and their “right” to endless material choice — Obama, like Gordon Brown, doesn’t have that option.

Since the New Economics Foundation and others published their Green New Deal back in July, there’s been growing interest in the U.K. in the idea that the economic crisis is not just an interesting precursor for the ecological crisis that will follow, but that in fact they are part of the same process of debt coming home to roost. Whatever the links, the fact that they coincide has major implications for the next decade of politics and business. One surprising outcome of a piece of research published by Forum for the Future at the end of 2008 is that consumer opinion may not be that important to business in the coming years. Or put another way, worrying what consumers think won’t get us out of trouble.

In “Acting Now for a Positive 2018,” [PDF] my colleagues David Bent and Joy Green developed four scenarios for business a decade hence . Even in the most soothing version of the future, the need to secure supply chains in the face of increasing competition for scarce resources will be a much greater driver of sustainability strategy than consumer concerns. In the more challenging scenarios, it is the defining agenda.

The same analysis argues for a new approach for government too, with sustainability firmly embedded at the heart of strategies for risk management, resilience, and security. Both Brown and Obama are talking this language, but in the U.K. engagement by different bits of government is patchy to say the least, and you don’t have to go far to find examples. The recent decision to go ahead with a new runway at Heathrow confirms a sense that aviation and roads orthodoxy still rules supreme at the Department for Transport.

Whether this new political language is populism or not is hard to judge. As recession bites here, there’s a growing sense that hard times will weed out the style and only those with substance will be left standing — businesses and politicians alike. But the fact is they’ll have to get the substance right, or end up faced with circumstances of financial and environmental austerity we can hardly imagine. And to avoid the worst case, waiting to see what the public thinks may be no use at all.

So, no pressure or anything, but it will be during Obama’s presidency that we find out what leadership for sustainability really means.