97% — Will Keir Starmer leave Prime Minister of the United Kingdom before Sep 1, 2026 Leader: Before Jul 1, 2026 at 97% · Kalshi 97% · 7 contracts · $149K volume · medium confidence Updated 2026-06-27 17:14:30 UTC Tracks the leading outcome in a winner-take-all prediction market set with 7 outcomes. Why this matters: Markets are currently pricing a 61% probability that Keir Starmer will leave his position as Prime Minister before September 1, 2026—roughly four months from now. This elevated probability reflects uncertainty about the sustainability of Labour's government following its 2024 election victory. The main drivers include Labour's relatively narrow working majority in Parliament, ongoing economic pressures, and potential internal party dynamics that could force leadership changes or trigger an election. Key catalysts would include significant by-election results, major policy failures, or shifts in Labour party cohesion. The timeframe is relatively short, meaning any departure would likely stem from immediate political crisis rather than normal electoral cycles. Market pricing suggests traders view near-term stability as contested but more likely than not to hold through summer. Key factors: - Labour's current House of Commons majority and the number of seats required to trigger a government collapse through defections or by-election losses - Economic indicators and public approval metrics in the UK between May and September 2026, as these typically drive confidence votes or election calls - Internal Labour party dynamics and any major policy implementation failures that could destabilize Starmer's position - By-election schedules and results that could shift the parliamentary arithmetic and pressure on government stability - External shocks or crises (economic, security, or political) that could accelerate leadership change timelines Contracts: - Will Keir Starmer leave Prime Minister of the United Kingdom before Jul 1, 2026?: Before Jul 1, 2026 — 97¢ Kalshi $69K (weight 46%) - Will Keir Starmer leave Prime Minister of the United Kingdom before Aug 1, 2026?: Before Aug 1, 2026 — 97¢ Kalshi $23K (weight 15%) - Will Keir Starmer leave Prime Minister of the United Kingdom before Jun 23, 2026?: Before Jun 23, 2026 — 96¢ Kalshi $21K (weight 14%) - Will Keir Starmer leave Prime Minister of the United Kingdom before Sep 1, 2026?: Before Sep 1, 2026 — 96¢ Kalshi $4K (weight 3%) - Will Keir Starmer leave Prime Minister of the United Kingdom before Jul 23, 2026?: Before Jul 23, 2026 — 95¢ Kalshi $18K (weight 12%) - Will Keir Starmer leave Prime Minister of the United Kingdom before Jul 24, 2026?: Before Jul 24, 2026 — 94¢ Kalshi $1K (weight 1%) - Will Keir Starmer leave Prime Minister of the United Kingdom before Jun 27, 2026?: Before Jun 27, 2026 — 92¢ Kalshi $14K (weight 9%) --- ## Methodology SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours. ## SF Signal - SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration. - No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only. --- *Last verified: 2026-06-23T07:20:51.227Z* By SimpleFunctions — https://simplefunctions.dev/ Cite as: "97% per prediction markets (SimpleFunctions, June 2026)" Canonical: https://simplefunctions.dev/answer/leavestarmer Full data: https://simplefunctions.dev/api/public/query?q=Will%20Keir%20Starmer%20leave%20Prime%20Minister%20of%20the%20United%20Kingdom%20before%20Sep%201%2C%202026 Provider: SimpleFunctions — https://simplefunctions.dev