**Green Party leader Zack Polanski’s high-profile candidacy consolidated left-leaning support in the former Labour stronghold of Holborn and St Pancras, driving the party’s vote share to 32.8% on 8 October 2026.** This represented a 22.4-point swing from the 10.4% recorded in 2024, partly by absorbing votes previously split with independent candidate Andrew Feinstein. Campaign emphasis on rent controls, climate action, and public ownership of utilities resonated in the inner-London constituency, building on recent Camden council gains. Lower turnout of 38.8% and a controversial party conference motion on Zionism limited further gains, while Labour retained the seat on 45.2% amid the transition to Prime Minister Andy Burnham. The outcome aligns with trader consensus on the 30-35% band and reflects the party’s strongest recent by-election performance short of a win.