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In this analysis
Germany's September state elections did more than punish Chancellor Friedrich Merz. They widened the distance between electoral arithmetic and the coalition conventions that have governed the Federal Republic. The AfD took first place in Mecklenburg-Western Pomerania, the Left won Berlin and the CDU recorded historically poor results in the east.
The result leaves mainstream parties with a harder institutional problem: maintaining exclusion rules around the AfD while assembling durable governments from an increasingly fragmented vote.
The firewall now carries a governing cost
The CDU's refusal to cooperate with the AfD limits the coalition combinations available after every strong AfD result. That may remain a principled democratic choice, but it means electoral growth for the party can constrain governments even without putting the AfD in office.
The Left's strength creates a mirror complication for conservatives. Parties can preserve red lines, but the arithmetic created by voters still determines how expensive those red lines become.
Merz's authority depends on delivery
Merz has said he intends to continue with tax and pension reforms despite the losses. That converts the next phase from an electoral argument into an implementation test. If reforms improve growth and household confidence, the centre can recover political room. If they impose visible costs before benefits arrive, fragmentation may deepen.
What changed
The centre has not disappeared, but it no longer controls the only plausible routes to power. Germany's political stability increasingly depends on whether established parties can make coalition constraints compatible with effective government.