The vote is the last test of the nation’s mood before the general election in September, in which Merkel will stand for the fourth time. The 13 million people eligible to cast their ballot in Germany’s industrial heartland on 14 May will offer the strongest indication yet as to whether Merkel can win, or whether the rival Social Democrats (SPD) might end her 11-year reign.
The SPD has put all its store by Martin Schulz, the former president of the European parliament, who unexpectedly swept on to the German political stage in January. Last month he was voted in as leader of the party and he is its challenger to face Merkel. His arrival created a surge in support for the SPD, causing its poll ratings to shoot up to a 10-year high, on a par with those of Merkel’s conservative alliance