By Laura Kuenssberg
Presenter, Sunday with Laura Kuenssberg
What's in vogue? Not just Labour leader Sir Keir Starmer in this month's glossy mag, or news that "discreet chic" is back and flamboyant "statement gowns" are out!
Politics has fashions too - what's in and out. It's not so long ago that world leaders were jostling to be pictured with celebs like Leonardo diCaprio, Stella McCartney or Emma Watson at the huge COP26 climate conference in Glasgow where Boris Johnson played host.
Then, it was hip to be green - being at COP in 2021 was the political equivalent of the fashion week front row. But with Labour shrinking away from its big £28bn commitments this week, and the Conservatives shifting tack and rumoured to be dropping the so-called "boiler tax", there's no doubt trends have changed.
Prime Minister Rishi Sunak took the first steps back in September. He didn't junk the government's green commitments but slowed the pace of existing plans.
Some Conservatives were delighted at he was heeding some voters' concerns about the cost of going green, most notably extending the ultra low emissions zone to outer London. Other Tories were infuriated it sent the message that the environment was less important, and that irritation has festered since then, with former minister Chris Skidmore quitting as an MP.
This week however it's been the Labour leadership's turn, finally getting rid of its vow to spend £28bn a year to help the country go green.
Without adding to the vast acreage of coverage about this decision, it shows above all that Labour wants to reassure voters it would be careful with their cash over anything else.
It's worth noting this week was the deadline for Labour's top team to give their manifesto plans to shadow chancellor Rachel Reeves.
The decision was finally made, after weeks of Tory taunting, when the sums actually had to add up. Alongside its manifesto, Labour will publish a "grey book" that will set out its exact spending plans.
So close to an election the view at the top is that every line of those calculations has to be accurate.
The leaderships of both main parties have moved, but there isn't agreement among their ranks either. On the right of the Conservatives, there's pressure on No 10 now to ditch the so called "boiler tax" - planned fines payable by boiler makers if they fail to hit targets for selling new heat pumps.
Former cabinet minister Robert Jenrick is one of those thundering about the risks of "dangerous green fantasy economics". But there's a pull from the other direction too.
The previously mentioned Chris Skidmore suggested that "if the UK does not step up, or turns its face against net zero opportunities, it would be an economic disaster".
In turn, Sir Keir Starmer's been accused by Labour former minister Barry Gardiner of being "economically illiterate and environmentally irresponsible".
Another of his MPs, Clive Lewis, responded to this announcement by tweeting a meme of Homer Simpson shrinking backwards into a hedge to describe how he'll feel on the doorstep talking to voters this weekend.
Others are frankly relieved the big number has gone, with one insider telling me it was "not our finest hour in terms of handling but we will look back and be really grateful that we did it".
What's not different?
While the parties' political attitudes have been shifting what has not budged at all is the obligations they face - not because of star-studded celeb pressure or activists gluing themselves to roads.
This is because, just before she left office, Theresa May changed the law in an absolutely profound way by introducing legislation that would force the UK to hit net zero by 2050.
In 2020 that was followed by another target to cut emissions by nearly 70% by 2030.
At the time the former PM pushed it through at breakneck speed 2050 seemed very far away. The practicalities of how such an ambition would be achieved were so vague that MPs (mostly) happily signed up.
One of those involved in the decision told me this week: "We thought it was the right thing to do but we understood we didn't have all the answers. It was a bit like when JFK said we are going to land a man on the moon at the end of the decade. He had no idea how he'd do it but it was a clear ambition."
- On this week's show will be Levelling-up Secretary Michael Gove and Labour's shadow chancellor of the Duchy of Lancaster Pat McFadden
- Actor Ralph Fiennes will be on to talk about his new production of Shakespeare's Macbeth, which opened this weekend
- Watch live on BBC One and iPlayer from 09:00 GMT and follow and stream here on the BBC News website
Despite shifting political passions that clear ambition and obligation has already had a major effect on what the government is actually doing.
One climate leader points to the package for cleaner steel at Port Talbot, or new laws on electric vehicles, for example, but adds that the government is "green hushing" - taking action but playing it down because "they don't want any coverage of it".
There is a definite sense in industry that politicians are yet to understand fully the scale of the changes that have to be made to reboot the energy system - the "transition".
Endless shifts in specifics of policies, or arguments about headline numbers risk missing the big picture. But with both the Conservatives and Labour grappling with the realities of what the big long-term commitments to net zero might really mean, perhaps what we are seeing is a new phase in this argument.
Polling consistently shows that action on climate change is near the top of voters' concerns - at number three on research group More In Common's list behind the cost of living and the health service, and not just among those on the left or the under-40s.
But as we move closer to the 2050 and 2030 targets the practical realities of the move to a greener economy will hit closer to home.
As one of the architects of the 2050 law, a former senior Conservative figure, said now "we've got to the point where it is starting to affect individual families it was always going to become politically contentious".
The public wants action generically, but might not like the effect of them - or as it was put to me: "Voters are allowed to be hypocrites - they can say 'I want you to do more' but then when you do, they say 'oh I didn't mean that'."
You can be horrified by what's happening to the planet round the world, but not be too eager to pay thousands for a new boiler at home.
There's a tension between how fast our two main parties are willing to move to tackle climate change and the rules and targets they set themselves.
But there is impatience in industry over how the appetite to act goes in and out of fashion, because much of the money to green the economy will come from them.
Maybe our conversations about the climate are becoming less about emotion and more about the economy. The problem is real. Now the political arguments are here to stay.