Sagal Abdi-Wali, the frontrunner for Labour’s nomination in the Holborn and St Pancras by-election triggered by Keir Starmer’s resignation, holds the highest implied probability at 44.5 percent on Polymarket, followed closely by independent Andrew Feinstein at 36.5 percent. The tightness stems from the seat’s 2024 result, where a left-wing independent took nearly 19 percent and the Greens 10 percent amid local dissatisfaction, combined with strong recent performance by Green and alliance candidates in Camden council wards. Zack Polanski’s likely Green candidacy and potential cooperation among progressive challengers add further uncertainty ahead of Labour’s candidate selection on 9 September and the Greens’ imminent process. Confirmation of final nominees, any formal pacts, and early campaign momentum on issues such as housing and foreign policy could quickly widen the gap among the leading contenders.