The party of Angela Merkel, Germany’s chancellor, suffered a setback on Sunday after Roland Koch, the Christian Democratic state premier of Hesse, saw his vote plummet following a closely watched regional election.

Yet the Social Democratic party, junior partner to Ms Merkel’s CDU in the “grand coalition” and its main rival in Sunday’s elections, had little to cheer about after the Left party, a radical leftwing grouping, captured a higher than expected share of the vote.