Zack Polanski lost the Holborn and St Pancras byelection to Labour's Sagal Abdi-Wali by 12 points — 45% to 33% — and the result lands as a stress test for a party that had been riding an extraordinary growth trajectory. Polanski framed it as a triumph: the Greens' second-best byelection result ever and a 13-point swing from Labour. His critics see something different — a leader with -28 net approval, now less popular than Nigel Farage, who has squandered the goodwill that quadrupled membership to over 230,000. The proximate damage is the Zionism-racism motion adopted at the Brighton conference. Polanski chose to campaign in Holborn rather than attend the debate, abstaining from both speech and vote. Former leader Caroline Lucas said publicly that he "should have been there and he should have voted." The leader of the Jewish Greens, Vivien Lichtenstein, called for his resignation outright. The motion equating Zionism with racism gave voters exactly the signal that soft Green supporters feared — that the party is drifting from environmental pragmatism into factional identity politics. Polanski's personal missteps compound the institutional problem. The unpaid council tax story, the shared social media post critical of police after the Golders Green stabbings — each individually minor, but cumulatively they've redrawn public perception. More in Common polling shows his net approval dropped four points to -28, making him the least popular major UK party leader. For a party whose appeal rested on being the unthreatening alternative to Labour's disappointments, that's structural damage. The Andy Burnham factor reshapes the competitive landscape. Labour's replacement of Keir Starmer with Burnham has brought disillusioned progressives back into the fold, closing the lane the Greens had been driving through. The Greens' national polling has fallen from 21% highs after Gorton and Denton to 10-11%. Luke Tryl of More in Common notes that the Holborn result was actually a decent one for Labour — the majority drop was below the postwar average for governing-party byelection defences. The party's left flank is holding firm. Greens Organise, the ecosocialist faction that backed Polanski's leadership bid, released a statement arguing that "not all growth and success is linear" and that Polanski remains "the leader who can get us there." Camden councillor Hamza Chowdhury — who was passed over as the Holborn candidate in favour of Polanski — called the result "a huge win." This internal narrative clash between pragmatists worried about electability and activists satisfied with directional progress is the fight that will define the party's next phase. The path forward is narrower than it was three months ago, but not closed. James Baggaley from UCL's Policy Lab argues the recovery route lies in returning to the economic messaging around "rip-off Britain" and generational fairness that originally powered the Green surge. Major Labour decisions on North Sea drilling and the budget could reopen the progressive flank. But the antisemitism question is a trust problem that messaging alone won't fix — it requires institutional action on conference governance and leadership accountability. The deeper question is whether the Greens' growth was a Polanski phenomenon or a structural realignment. If membership quadrupling and Gorton and Denton were products of Labour's weakness under Starmer rather than Green strength, then Burnham's arrival may have closed the window regardless of who leads. If the Greens built genuine institutional capacity during the surge, a leadership change could unlock it. The next six months — budget fallout, drilling decisions, internal governance reform — will answer that question.
