Peer Steinbrueck, the SPD candidate for chancellor, is trailing badly in opinion polls, but his rhetorical gifts could give him an edge over Mrs Merkel in their only televised showdown before the September 22 election. He could also be helped by the inclusion of an irreverent entertainer on the question panel.
Mr Steinbrueck has promised to confront Mrs Merkel over bailouts to Greece, but will also want to avoid appearing too aggressive in the prime-time clash.
The former finance minister has a quick wit, but can appear arrogant and overbearing and, like US Republican challenger Mr Romney, polls show he suffers from a "likeability" problem.
The challenger said yesterday: "I don't need to rehearse. My appearances are more interesting and lively than Frau Merkel's. With me, it rocks."
Mr Steinbrueck's has also promised to take his wife's advice ahead of the face-off. Gertrud, a schoolteacher, has suggested he take deep breaths before launching into critiques of Mrs Merkel.
Adding a twist to the debate is Stefan Raab, one of Germany's most popular entertainers, who will join more traditional TV anchors on the panel that will quiz the candidates.