As strange as it may sound, for the next few weeks, the future of left-of-centre politics might revolve around a verdant corner of west London, where a trailblazing step into a better future has been taken by two underrated revolutionary organisations, the Richmond and Twickenham branch of the Green party, and its counterpart in Kingston-upon-Thames.

For the last week or so, a loud debate has raged about the looming Richmond Park byelection, and how the various non-Tory parties ranged against the faux-independent Zac Goldsmith should respond to a contest called at his behest. He wants everything to be focused on his opposition to Heathrow expansion, but the vote that will happen on 1 December is inevitably about much more, not least because of Goldsmith’s belief in Brexit and the high court’s decision about parliament’s role. In that context, the people of Richmond Park have a simple enough choice: should they return someone who will view a vote on article 50 as a chance to hold the government to account, avoid hard Brexit and even push for a second referendum? Or do they prefer a convinced leaver who is likely to approach things from the opposite standpoint?

Labour managed to get 12% of the local vote in 2015; in 2010, when the Liberal Democrats lost the seat to Goldsmith and the Tories, it was on a princely 5%. In the last week, a few high-profile Labour people have made the case for their party standing down in favour of Tim Farron’s lot, but they are up against the various strands of their party still united by their undying tribalism, up to and including the supposedly radical party leadership.

At the same time, with an apparent reluctance, the local Greens – who got 6% last time – decided they should field a candidate (their conclusion, said the party’s co-leader Caroline Lucas, was that “it would be difficult not to field a candidate unless Labour did the same”), before changing their minds. Now, the two relevant party branches have commendably decided to bow out, and give the Lib Dems a clearer run.

The Lib Dems ought to honour the Greens’ move by sooner or later giving something back in kind. Labour, meanwhile, is set to formally pick its candidate this Saturday. Given deep divisions in the party about whether Brexit is to be questioned, the high court decision will throw it into a spin, and colour its approach to what it does in Richmond Park. But if Labour were collectively clever, it could view a defeat for the government as the key priority, stand down with honour, and demand a clear payback. That payback could be, for example, the Lib Dems backing off at the next election (which may come sooner than some people think) in nearby Brentford and Isleworth, where the boot is on the other foot: in 2015, Labour won the seat with 43.8% of the vote to the Tories’ 42.9%, with the Lib Dems and Greens between them polling just under 8%.

So why not? Bound up with all that tribalism, there is a deep conviction that the Lib Dems remain Conservatives by any other name, so untouchable that the better option is to hand a Tory a win. To that, there is one obvious response: a sigh of frustration, and a reminder that we are now in the Brexit age, where the record of Nick Clegg et al might still understandably rankle, but there are much, much bigger things at stake.

We all know the most likely outcome of our current political and economic turbulence: the mean, crabby, low-tax, light-regulation Tory/Ukip vision of Britain’s future. If you want any kind of alternative – some salvaged relationship with Europe, a better tenor of debate, and renewed hope for progressive politics in England – there is only one way to get it: the Tories and their allies have to be beaten, at every available opportunity. A seat largely in a borough that voted 70% for remain, where the sitting MP is an enthusiastic Brexiteer, surely represents an ideal opportunity. But rather than the fragile comfort of tactical voting, that prospect requires something game-changing, and symbolic.

There is another strand to this story, which is to do with the wider social climate, and the fact that in the wake of the referendum, the political discourse in England seems to get grimmer every day. Last summer, Goldsmith’s campaign for the London mayoralty was an augury of what was to come: a low, shameless quest to associate Sadiq Khan with militant Islam, tap into fears supposedly coursing around the suburbs, and clinch a win. If he had been successful, the upshot would have been a huge warning sign standing in the way of anyone Muslim standing for public office – but in the post-referendum climate, who would be surprised if similar campaigns are waged again and again? Richmond Park offers a chance to underline the awfulness of what Goldsmith did – and the fact that it ought to be avenged not once, but twice.

By a mixture of accident and design, the right of British politics is healing up, for the moment at least. In the latest Guardian/ICM poll, the Tories are on 43% in the polls to Labour’s 27%, while Ukip looks to be imploding (by way of saving money and cementing what some people call the “regressive alliance”, it has pledged its support to Goldsmith, and decided not to run a candidate at the byelection).

On the liberal left, by contrast, the picture is of division and looming defeat, even as large swaths of activists from Labour, the Lib Dems, the Greens, and the nationalist parties increasingly share many of the same priorities: not just opposition to hard Brexit – or Brexit, period – but a belief that we need to change our rotten voting system, so as to ensure that further calamities don’t happen in the future. Endless defeat is not the way to advance those causes. Dialogue and cooperation are the key, coupled with a much smarter approach to electoral politics.

To use the term put on the agenda by the cross-party left-leaning pressure group Compass, we need a progressive alliance. If the idea is to have any mileage, it will have to be manifested in local initiatives rather than top-down edicts – and in that sense, there is a flavour of the future in the fact that the Greens’ move has come not at the insistence of the national leadership, but thanks to a change of heart by grassroots activists.

Whenever the next election arrives, people need to be pressuring parties into operating in new ways, and making clear that the urgency of the moment demands nothing less. The Greens have just done exactly that, and pointed the way. As they probably say in Richmond, bravo.