Local council · West Sussex
Horsham Riverside
1 seat contested on Thursday 7 May 2026. 6 candidates from 6 parties.
Predicted vote share
What the model expects
Predictions are point estimates: the model's best guess, not a guarantee. The "How this prediction was made" section below lists every step that shaped this forecast.
How accurate was the model here?
Our 7 May 2026 forecast for Horsham Riverside
✗ Winner missed
, predicted Reform UK,
actual Lib Dem.
Major-party MAE: 7.74pp
across the parties below.
| Party | Predicted | Actual | Gap |
|---|---|---|---|
| Reform UK | 35.5% | 21.6% | +13.9pp |
| Labour | 6.6% | 3.6% | +3.0pp |
| Conservative | 16.6% | 15.6% | +1.0pp |
Positive gap = we predicted that party would win more share than they did. See the full West Sussex accuracy summary or the national audit.
Recent contests
What happened last time
| Date | Type | Winner | Top share | Source |
|---|---|---|---|---|
| 2025-05-22 | By-election | Lib Dem | 45.7% | declaration |
| 2021-05-06 | Cycle | Lib Dem | 46.0% | declaration |
| 2017-05-04 | Cycle | Lib Dem | 43.6% | declaration |
Candidates 2026
Parties on the ballot
- Conservative and Unionist Party
- Green Party
- Labour Party
- Lib Dem
- Reform UK
- The Peace Party - Non-violence, Justice, Environment
How this prediction was made
- Baseline . Most recent borough result (2025-05-22)
- National Swing (STM) . Strong Transition Model: multiplicative bounded swing, dampened by 0.1 for local
- Demographics . No significant demographic adjustments for this ward
- Incumbency . No current holder data available
- New Party Entry . Reform UK has existing baseline, no proxy needed
- Normalise . All shares scaled to sum to 100%
- Restrict to ballot . Removed 3 party/parties not standing in 2026 (SNP 0.0pp, Other 0.0pp, Plaid Cymru 0.0pp). Their share redistributed pro-rata.
- 2025 county-cycle anchor . No 2025 reference available for this council's parent area. Stage 1 uses national polling only.
- Reform realignment uplift (no-anchor councils) . No 2025 parent-county anchor available; demographic-borrow rule applied. Asian 3.0% → base target 36.0% × regional multiplier 0.85 = 30.6%. Reform 19.4% → 30.6% (lift +11.2pp). Other parties scaled pro-rata. Calibration source: Burnley 2026 ward-level Asian%↔Reform% relationship (the 2-tier district that did receive the LCC 2025 anchor).
- National-share calibration . Aggregate-predicted vs national-polled mismatch corrected at strength 0.65. Multipliers — Labour ×0.82, Conservative ×1.00, Reform UK ×1.15, Liberal Democrats ×0.96, Green Party ×1.12, SNP ×1.00, Plaid Cymru ×1.00.