German election: Merkel and Schulz to face off in TV debate

Martin Schulz of the Social Democratic Party will be trying to set a distinct agenda from the Christian Democratic Union's Angela Merkel.

(CNN)The German election is very much Chancellor Angela Merkel's to lose. But Sunday evening's encounter with her principal opponent -- the sole head-to-head debate of the campaign -- is a moment of potential peril.

Few leaders in the democratic world can match Merkel's experience -- she has led Europe's biggest economy for more than 11 years and polls show her Christian Democratic Union Party (CDU) as the clear frontrunners for the September 24 vote.
There are very few threats to Merkel "sleepwalking" through this election -- as German media puts it -- but this debate could be one of them.