Zack Polanski's leadership of the Green Party follows a pattern familiar to protest movements across democracies: build support by positioning against an unpopular establishment figure, then watch that support evaporate the moment the establishment adapts. The Greens climbed to 18% in the polls and won the Gorton and Denton byelection against Matt Goodwin while Keir Starmer was Labour leader. Then Starmer was replaced by Andy Burnham, a communicator voters were willing to give a chance, and the Greens cratered to 11%. Polanski's net approval rating now rivals Nigel Farage's — a remarkable collapse for someone who a year ago was riding the highest Green polling in British history. His decision to stand in the Holborn and St Pancras byelection looks increasingly like a strategic miscalculation. His own team briefed journalists at the Brighton conference that even if they persuaded 30% of Labour voters to switch, he would still lose by four points. That is not expectation management; it is triage. The Brighton conference itself was a study in institutional denial. Polanski didn't want it to happen, preferring to concentrate on his byelection campaign. Senior leadership figures briefed that the whole event was pointless. It went ahead anyway, opening with MPs Siân Berry and Hannah Spencer performing the kind of manic enthusiasm that reads as compensation rather than confidence. Polanski's leader's speech — roughly half the customary length — drew precisely two standing ovations: one for saying "Palestine" and one for "green revolution." In Brighton, those are reflexes, not endorsements. The speech offered the standard menu — taxing the rich, rent controls, environmentalism — but with no costings, no implementation detail, no sense of how slogans translate into governance. "I say to government, 'Slogans aren't enough,'" he said, apparently without irony. The structural problem for the Greens is that their recent growth was almost entirely parasitic on Labour's weakness rather than generative of independent political capability. They built no durable institutional infrastructure, no policy apparatus that could survive the loss of their anti-Starmer positioning. When the host organism adapted, the parasite starved. Polanski came across, in the words of the room, as a "rather shouty undergraduate student" — long on agitprop, short on genuine argument. Previous leaders like Caroline Lucas and Carla Denyer projected substance even when the party was smaller. Polanski projected energy, which is a depreciating asset in politics. The arms-aloft triumph at the end, staged by Berry and Spencer, read as valedictory rather than victorious. If he loses Holborn and St Pancras, the leadership question becomes immediate. But the deeper question is whether the Greens can build something that doesn't depend on Labour being bad at its job — whether they can generate their own political value rather than extracting it from someone else's failures.
