Parliamentary Coalition & Majority Builder
Simulate vote-share shocks, electoral hurdle cutoffs, Sainte-Laguë seat allocations, and coalition stability buffers across fragmented parliaments.
Election Inputs
Plenary Hemicycle & Seat Distribution
Majority: 61 / 120Calculated Coalition Combinations
Combinations reaching the governing majority line (50% + 1 seat) based on current seat allocations.
| Coalition Formula | Parties | Seats | Seat % | Majority Buffer | Status | Action |
|---|
The Mathematics of Coalition Shocks
Sainte-Laguë / Schepers Seat Allocation
German federal (Bundestag) and state (Landtag) elections allocate seats to qualifying parties using the divisor method with standard rounding (divisors 0.5, 1.5, 2.5, ... or 1, 3, 5, ...). It avoids systemic bias toward large or small parties and guarantees strictly proportional representation.
The Electoral Hurdle (Sperrklausel) Cascade
When smaller parties (like FDP, Left, or BSW) dip below the 5% barrier, all their popular votes are excluded from seat allocation. This effectively lowers the absolute vote percentage required for remaining parties to secure an outright parliamentary majority, drastically reshuffling coalition leverage.
Defection Buffers & Stability
In parliamentary systems, a chancellor or minister-president requires a stable majority for investiture and confidence votes. A narrow majority (+1 or +2 buffer) creates catastrophic fragility where single backbench defectors or illness can paralyze legislation.
Cordon Sanitaire & Blocked Majorities
When radical-right or populist parties capture over a third of parliamentary seats ("blocking minority"), standard two-party coalitions often become mathematically impossible, forcing ideologically divergent multi-party alliances (e.g. Kenya, Black-Red-Purple) or fragile minority administrations.