US House Redistricting
When redistricting is enabled, US House elections resolve per congressional district instead of statewide proportional allocation. Each district has its own lean derived from a 16-square voter map; a party holding a state trifecta (governor plus chamber majority from the same party) can redraw that map between cycles.
District maps#
Each state's House delegation is represented as N districts × 16 squares. Every square is tagged left, right, or grey (swing). District lean comes from the square mix: a district heavy on right squares is safer for Republicans; packed left or right squares create lopsided seats.
House races in a redistricted state run one election per district. Candidates compete for a single seat using the same vote-accumulation engine as other races, but the underlying electorate is the district's lean, not the whole state average.
Who can draw maps#
Map authority depends on state legislation (three policy levers):
| Law | Options | Effect |
|---|---|---|
| Redistricting authority | Independent commission / Bipartisan commission / Legislature-drawn | Only legislature-drawn maps can be gerrymandered by the trifecta holder; commissions block partisan draws |
| Compactness | Strict / Moderate / Loose | Caps how far any district's lean may deviate from the state mean |
| Fairness | Strict / Moderate / Loose | Caps the statewide efficiency gap (a measure of wasted votes across districts) |
A trifecta (same party controls the governorship and the state legislature majority) is required to open the map editor in legislature-drawn states.
Drawing rules#
Proposed maps must satisfy all active caps:
- Each district totals exactly 16 squares (no negative counts).
- Statewide square totals are conserved: you redistribute voters, not invent them.
- Per-district deviation: no district may lean more than the compactness tier allows away from the state mean.
- Packed districts: districts with ≥12 squares of one color count toward a packed-district limit.
- Efficiency gap: the statewide gap between wasted left and wasted right votes must stay below the fairness ceiling.
Illegal maps cannot be saved. Auto-map presets respect the same legality checks: strategies blocked by current law are disabled in the UI.
Map editor tools#
Trifecta holders use the state redistricting editor to:
- Drag squares between districts manually.
- Apply auto-map strategies (maximize seats, neutralize, protect incumbents, etc.) within legal caps.
- Review a composition summary: seat lean breakdown, compactness indicators, and efficiency-gap readout before committing.
Committed maps take effect for the next House cycle in that state.
Campaign effects#
District-level races mean ground game and ads target a smaller electorate. Statewide popularity still matters, but winning a gerrymandered map often requires contesting the handful of grey or lightly leaning districts rather than running up margins everywhere.
Related#
- Election Mechanics: vote accumulation and FPTP resolution
- General Elections: closing-sprint tactics at district scale
- Demographics: how state texture feeds district leans
- Bills & Legislation: state redistricting, compactness, and fairness laws