Zack Polanski hails seismic year - but awkward polls suggest Green Party bubble has burst

By all rights this year's Green Party conference in Brighton should be the biggest celebration in its history. Just six months ago Zack Polanski and co sent a shockwave through UK politics and sped up Keir Starmer's demise by winning the Gorton and Denton by-election. In doing so, they showed they could overturn a huge Labour majority in a historically safe seat - and put dozens of Labour MPs on notice. It was a seismic moment that suggested the Greens - having already secured a record four MPs at the general election - could help shatter the two-party system in place for over a century. But roll forward to October and things are looking less rosy. The bump in the polls has largely subsided, and Mr Polanski's own ratings are not where he'd like them to be. On Thursday next week the leader faces a reckoning in the Holborn and St Pancras by-election, triggered by Keir Starmer's unexpected resignation as an MP. To be clear, a Green victory here would be monumental - the former PM secured an 11,000 majority and the seat has been a Labour stronghold for decades. As one Green spinner put it, the fact that we're even talking about Mr Polanski being in a two-horse race is a sign of how far the party has come. In 2024 Mr Starmer picked up over 18,800 votes, while the Greens received just 4,000. If he does fall short, Mr Polanski can take heart - but some within the party may quietly wonder what might have been. In spite of some very considerable gains over the past year, latest polling does suggest the Green bubble has burst. In early March polls put them on around 21% of the overall vote - some even suggesting they were challenging for second place. Those heady days feel a long time ago now, though, with most pollsters placing them around the 11% mark and back down in fifth. Is the party a victim of its own success? By winning in Gorton and Denton, it set off a chain of events that significantly weakened Mr Starmer and contributed to his decision to resign. Now Andy Burnham is making the kind of arguments left-wing voters want to hear, for example on the Middle East, nationalisation and Brexit. His barnstorming speech at the Labour conference on Tuesday highlighted a party that has its mojo back after a couple of troubled years. This is squeezing the Greens, and YouGov polling this week showed that over the course of Mr Polanski’s leadership, the party's net favourability rating has fallen from +5 to -19. And so we find ourselves at the Green Party conference in Brighton this weekend with a lot at stake. Mr Polanski has decided his most effective gambit is to claim credit for the government's change in direction - and suggest the Greens can push Labour even further. In his conference speech on Friday, he argued that electing him as an MP will send a message to the government not to get complacent. "Vote Green, and watch Labour move," he said. "Voting Green, between general elections, is the most powerful vote you can make. At general elections, the government changes. But between general elections – we change the government." On recent form it's hard to argue with that. But now Mr Starmer has gone, does Labour still face the same danger from the left? The Greens argue yes, saying Mr Burnham still needs to deliver on his promises - and pointing to their own policy offerings. These include protections against rent rises, immediately bringing water companies into public ownership and de-proscribing Palestine Action. Mr Polanski undoubtedly has an energetic support base, with activists giving ovation after ovation during his speech. Speaking afterward, Gorton and Denton's Green MP Hannah Spencer told The Mirror that the mood is upbeat. She said: "It's just unbelievable. When you think back to this time last year, and we were celebrating Zack becoming leader, like this huge boost in members, and members who were really keen and want to get involved, there's just been this shift about people coming and joining the party who realise that there is like a hopeful movement that we're building. "And when things feel really scary in the world, there is something that we can do to change it. And we've got a lot of wins to celebrate." If Mr Polanski adds another win on Thursday, it would be a historic upset that would eclipse even Gorton and Denton. Insiders insist it's all to play for, and Green campaigners have been encouraged to miss the conference in order to join a final push in North London. But if it doesn't go well, next year's conference will feel a lot different.