For a quarter of a century, Manfred Güllner has kept his finger on the pulse of German public opinion. Yet in all these years, the founder of the Forsa polling institute says he has come across nothing as curious as the current state of the country’s Social Democratic party.

Germany’s oldest party and still just the largest by membership has run or participated in governments without interruption for the past 10 years but is now “in an utterly desolate shape”, according to the veteran pollster. “It is essentially in the process of destroying itself.”