The textbook definition of a coalition government is simple enough: two or more parties share power because none commands a majority alone. What the textbooks rarely explain is why some of these marriages of convenience last a full parliamentary term while others disintegrate before the ink dries on the coalition agreement. The answer lies not in ideology or policy compatibility, but in the unglamorous architecture of mutual dependency.
Coalition survival is, at its core, an exercise in making defection more expensive than cooperation. Every successful multi-party government in modern democratic history has understood this, whether consciously or through trial and error.
The portfolio allocation game
The first and most consequential negotiation in any coalition is not about policy—it is about ministries. Who controls finance? Who gets foreign affairs? The distribution of cabinet portfolios determines which party can claim credit for popular policies and, crucially, which party will be blamed when things go wrong.
Germany's postwar coalitions have elevated this to an art form. The smaller coalition partner traditionally receives ministries with high visibility but limited downside risk—foreign affairs, for instance, where a competent minister can accumulate prestige without being blamed for domestic economic pain. The larger party absorbs the finance ministry, accepting greater risk for greater reward. This asymmetry creates stability: the junior partner has enough to show voters, while the senior partner maintains control over the levers that matter most.
Israel's coalitions, by contrast, frequently collapse because portfolio allocation becomes a zero-sum scramble. Small religious parties demand control over education or interior ministries that allow them to deliver tangible benefits to their narrow constituencies. When those benefits conflict with the broader coalition's agenda, the government fractures.
The confidence-and-supply alternative
Not all coalitions require full partnership. The confidence-and-supply arrangement—where a party agrees to support the government on budgets and no-confidence votes without joining the cabinet—offers an escape valve for parties that cannot stomach formal alliance.
This model dominated Irish politics for decades and has appeared in various forms across Scandinavia. Its advantage is flexibility: the supporting party can oppose specific legislation without bringing down the government. Its weakness is that it creates a permanent state of negotiation. Every major bill becomes a fresh opportunity for extraction, and the government operates in a perpetual hostage situation.
Why ideological distance matters less than you think
Conventional wisdom holds that coalitions between ideologically distant parties are doomed. The evidence suggests otherwise. Germany's grand coalitions between the center-left SPD and center-right CDU/CSU have repeatedly proven more durable than coalitions between closer ideological neighbors. The reason is counterintuitive: when parties are far apart, they occupy distinct electoral niches. Neither can credibly steal the other's voters, so neither has incentive to sabotage the partnership for short-term gain.
Coalitions between adjacent parties—center-left with left, center-right with far-right—face constant temptation. The junior partner fears absorption; the senior partner fears being outflanked. Every policy compromise becomes an existential threat to someone's voter base.
Our take
The durability of coalition governments has little to do with the high-minded compromises that politicians celebrate in signing ceremonies. It has everything to do with whether the architecture of the agreement makes betrayal costly and loyalty rewarding. The most stable coalitions are not those where partners agree on everything, but those where partners need each other in ways they cannot easily escape. This is not cynicism—it is the honest mechanics of shared power, and understanding it explains more about parliamentary democracy than any amount of policy analysis ever could.
