Which party will win the Holborn and St Pancras by-election?

## Cross-Market Signals

### Polymarket
- "Will the Moderate Party (M) win the second most seats in the 2026 Swedish parliamentary election?" → Yes: 1.00, Volume: $174.4K
- "Will the Moderate Party (M) win the third most seats in the 2026 Swedish parliamentary election?" → Yes: 0.00, Volume: $111.4K

1. [sq2 | wikipedia_lookup | STRONG cred 92 | NEUTRAL | RECENT] By-election set for 8 October 2026 after Starmer resigned on 1 September; writ moved 7 September, nominations close 15 September.
2. [sq2 | question_description | STRONG cred 95 | UP | DATED] At the 2024 general election Labour won 48.9%, independent Andrew Feinstein 18.9%, Greens 10.4%; seat has never been won by a non-Labour party.
3. [sq1 | web_search | MODERATE cred 82 | UP | VERY_RECENT] Green members backed party leader Zack Polanski as candidate and he has confirmed his candidacy, prompting bookmakers to shorten Green odds.
4. [sq2 | web_search | MODERATE cred 72 | UP | VERY_RECENT] Bookmakers price Labour at roughly 1/3 to 2/5 (about 70-80% implied) and Greens at 5/2 to 3/1 (about 25-33%).
5. [sq1 | web_search | WEAK cred 55 | NEUTRAL | VERY_RECENT] Oddschecker reports 64-75% of recent bets backed the Greens despite Labour remaining heavy favourite.
6. [sq1 | web_search | MODERATE cred 68 | DOWN | VERY_RECENT] National Green polling has fallen roughly a third since Burnham became PM; Polanski's net approval dropped from -13.4 (April) to -24.3 (September).
7. [sq2 | article_search | MODERATE cred 78 | UP | RECENT] Andy Burnham became PM in July 2026, is more popular than Starmer, and won his own by-election return to Parliament this summer.
8. [sq2 | question_description | MODERATE cred 85 | NEUTRAL | VERY_RECENT] Labour has selected Camden councillor Sagal Abdi-Wali as its candidate.
9. [sq4 | web_search | MODERATE cred 70 | DOWN | VERY_RECENT] Bookmakers price all parties other than Labour and Greens at 100/1 or longer.
10. [sq3 | web_search | WEAK cred 40 | NEUTRAL | VERY_RECENT] No research surfaced whether Andrew Feinstein or any left-independent will stand; final candidate list awaited after 15 September nominations close.
11. [sq1 | article_search | WEAK cred 50 | NEUTRAL | DATED] Reform UK reported Polanski to police in July 2026 over an Instagram post; Greens dismissed it as performative outrage.
12. [sq4 | article_search | WEAK cred 65 | NEUTRAL | RECENT] Reform UK faces a police investigation into impermissible donations; Farage won Clacton by-election in August after mainstream parties boycotted.

## Cross-Market Signals

### Polymarket
- "Will the Moderate Party (M) win the second most seats in the 2026 Swedish parliamentary election?" → Yes: 1.00, Volume: $174.4K
- "Will the Moderate Party (M) win the third most seats in the 2026 Swedish parliamentary election?" → Yes: 0.00, Volume: $111.4K

Information gaps:
  - No constituency-specific polling found for Holborn and St Pancras
  - Base rate: how often governing party holds seat in by-election shortly after new PM honeymoon
  - Whether Feinstein or Your Party/left-independent candidates stand (nominations close 15 Sept)
  - Local Camden council election results and recent London Green performance

Key uncertainties:
  - Whether Feinstein's 2024 anti-Labour vote consolidates behind Polanski or fragments
  - Durability of Burnham honeymoon and Labour national recovery through 8 October
  - Turnout profile in low-salience October by-election
  - Impact of party-leader candidacy drawing national Green resources and media

You are an elite superforecaster. Estimate the probability of each option for this Metaculus multiple-choice question.

## Question
Which party will win the Holborn and St Pancras by-election?

## Description / Resolution Criteria
## Description
A by-election is due to take place in [Holborn and St Pancras](https://en.wikipedia.org/wiki/2026_Holborn_and_St_Pancras_by-election) following the resignation of former Prime Minister Keir Starmer from the House of Commons on 1 September 2026.

The constituency is an inner London seat covering parts of the London Borough of Camden. At the 2024 general election, Labour won the seat with 48.9% of the vote, although its vote share fell substantially compared with the previous election. Independent candidate Andrew Feinstein finished second with 18.9%, while the Green Party finished third on 10.4%.

Labour [has selected](https://www.standard.co.uk/news/politics/sagal-abdiwali-labour-favourite-holborn-byelection-keir-starmer-b1296058.html) councillor Sagal Abdi-Wali to be their candidate.

The Green Party has attracted particular attention ahead of the by-election. Party members [have backed](https://www.theguardian.com/politics/2026/sep/11/zack-polanski-selected-green-party-holborn-st-pancras-byelection) their leader, Zack Polanski, to seek the party's nomination. 

## Resolution Criteria
This question will resolve as the political party of the candidate officially declared elected as Member of Parliament for the Holborn and St Pancras constituency in the 2026 by-election.

## Fine Print
* If a candidate of a party not listed, or an independent candidate wins, the question will resolve as Other.
* If a candidate changes party affiliation after nominations close but before taking their seat, the party listed on the official election result will determine resolution.
* If the by-election is cancelled because of a general election, constituency abolition, or another electoral event that prevents the by-election from taking place, the question will be annulled.

## Options
  - Other
  - Labour Party
  - Green Party

## Sub-question decomposition (planner)
- (w=0.35) Will the Green Party candidate (Zack Polanski, if selected) win the Holborn and St Pancras by-election?  — The Greens are the principal challenger given Polanski's national profile, the 2024 anti-Starmer left vote (Feinstein 18
- (w=0.35) Will Labour's candidate Sagal Abdi-Wali hold the seat for Labour?  — Labour starts with a 30-point 2024 margin and a strong local machine, but governing parties suffer heavy by-election swi
- (w=0.15) Will Andrew Feinstein or another independent/left-independent candidate stand and finish first or second, fragmenting the anti-Labour vote?  — Feinstein came second in 2024; if he stands again the anti-Labour vote splits (helping Labour), if he endorses the Green
- (w=0.15) Will Reform UK, the Conservatives, or the Liberal Democrats be polling within 10 points of the leader in constituency-specific polling before close?  — Inner London Camden is very unfavourable ground for Reform/Tories/LDs, but national Reform surges and vote fragmentation

## Synthesized evidence
1. [sq2 | wikipedia_lookup | STRONG cred 92 | NEUTRAL | RECENT] By-election set for 8 October 2026 after Starmer resigned on 1 September; writ moved 7 September, nominations close 15 September.
2. [sq2 | question_description | STRONG cred 95 | UP | DATED] At the 2024 general election Labour won 48.9%, independent Andrew Feinstein 18.9%, Greens 10.4%; seat has never been won by a non-Labour party.
3. [sq1 | web_search | MODERATE cred 82 | UP | VERY_RECENT] Green members backed party leader Zack Polanski as candidate and he has confirmed his candidacy, prompting bookmakers to shorten Green odds.
4. [sq2 | web_search | MODERATE cred 72 | UP | VERY_RECENT] Bookmakers price Labour at roughly 1/3 to 2/5 (about 70-80% implied) and Greens at 5/2 to 3/1 (about 25-33%).
5. [sq1 | web_search | WEAK cred 55 | NEUTRAL | VERY_RECENT] Oddschecker reports 64-75% of recent bets backed the Greens despite Labour remaining heavy favourite.
6. [sq1 | web_search | MODERATE cred 68 | DOWN | VERY_RECENT] National Green polling has fallen roughly a third since Burnham became PM; Polanski's net approval dropped from -13.4 (April) to -24.3 (September).
7. [sq2 | article_search | MODERATE cred 78 | UP | RECENT] Andy Burnham became PM in July 2026, is more popular than Starmer, and won his own by-election return to Parliament this summer.
8. [sq2 | question_description | MODERATE cred 85 | NEUTRAL | VERY_RECENT] Labour has selected Camden councillor Sagal Abdi-Wali as its candidate.
9. [sq4 | web_search | MODERATE cred 70 | DOWN | VERY_RECENT] Bookmakers price all parties other than Labour and Greens at 100/1 or longer.
10. [sq3 | web_search | WEAK cred 40 | NEUTRAL | VERY_RECENT] No research surfaced whether Andrew Feinstein or any left-independent will stand; final candidate list awaited after 15 September nominations close.
11. [sq1 | article_search | WEAK cred 50 | NEUTRAL | DATED] Reform UK reported Polanski to police in July 2026 over an Instagram post; Greens dismissed it as performative outrage.
12. [sq4 | article_search | WEAK cred 65 | NEUTRAL | RECENT] Reform UK faces a police investigation into impermissible donations; Farage won Clacton by-election in August after mainstream parties boycotted.

## Cross-Market Signals

### Polymarket
- "Will the Moderate Party (M) win the second most seats in the 2026 Swedish parliamentary election?" → Yes: 1.00, Volume: $174.4K
- "Will the Moderate Party (M) win the third most seats in the 2026 Swedish parliamentary election?" → Yes: 0.00, Volume: $111.4K

Information gaps:
  - No constituency-specific polling found for Holborn and St Pancras
  - Base rate: how often governing party holds seat in by-election shortly after new PM honeymoon
  - Whether Feinstein or Your Party/left-independent candidates stand (nominations close 15 Sept)
  - Local Camden council election results and recent London Green performance

Key uncertainties:
  - Whether Feinstein's 2024 anti-Labour vote consolidates behind Polanski or fragments
  - Durability of Burnham honeymoon and Labour national recovery through 8 October
  - Turnout profile in low-salience October by-election
  - Impact of party-leader candidacy drawing national Green resources and media

## Required pre-forecast walkthrough

Before giving probabilities, address these explicitly in your rationale:
  (a) The time left until the question resolves.
  (b) The status quo outcome — the option most likely if nothing changes from today.
  (c) An outcome that would be SURPRISING but plausible.

## Calibration guidance

- **Status quo anchoring.** Good forecasters put extra weight on the status quo option because the world changes slowly most of the time.
- **Leave moderate probability on most options.** Good forecasters don't drop options to ~0% — leave ≥3-5% on every option to account for unexpected outcomes, unless you have strong specific evidence ruling them out.
- Avoid uniform-distribution laziness — most options are not equally likely.
- **Anchor on prediction markets.** If liquid market prices (Polymarket / Kalshi) for these options appear in the evidence, treat them as a strong prior and stay close to them absent specific contrary evidence.

## Output

Return ONLY valid JSON, no markdown fences:

{
  "rationale": "<address (a) (b) (c) above, then explain your distribution — 4-7 sentences total>",
  "probabilities": {
    "Other": <prob>,
        "Labour Party": <prob>,
        "Green Party": <prob>
  }
}

Probabilities MUST sum to ~1.0 (renormalization is applied; close enough is fine).