Armin Laschet, the conservative candidate and Angela Merkel's replacement at the head of the CDU, faced the Social Democrat's Olaf Scholz and the Green's Annalena Baerbock. This was the second in a set of three debates, with the final showdown set to take place on September 19 ahead of polling day in Germany on September 26.

       Mr Laschet had hoped to use this opportunity to turn around what has already been a damaging campaign for the CDU.

       But his hopes were dashed when, despite a heavy grilling from his conservative counterpart, the centre-left Scholz emerged as victor.

       A snap poll after the debate showed Mr Scholz, the current finance minister, had beaten his opponents to win the debate, adding another feather to his cap in the race to take over as German chancellor.

       The poll for ARD television taken soon after the 90-minute debate showed that 41 percent of those asked thought Mr Scholz was the most convincing performer, compared to 27 percent for Mr Laschet and 25 percent for Ms Baerbock.

       READ MORE: Germany election polls: Merkel's CDU has worst poll results since 1984

       Mr Scholz's SPD has enjoyed a firm lead in the polls during the election campaign, leaving the CDU lagging behind with some of its worst ratings in over 50 years.

       The SPD candidate maintained his lead by weathering attempts from Mr Laschet to discredit his opponent's reputation.

       Mr Laschet accused Mr Scholz of failing in his supervision responsibilities in light of raids last week on the finance and justice ministries that were part of an investigation into the government's anti money-laundering agency.

       Mr Laschet said: "If my finance minister were to work like you, then we would have a serious problem."

       But Mr Scolz was unruffled, accusing his opponent of twisting facts and being "dishonest" by suggesting there was a probe of his ministry, whereas investigators simply needed information from it.

       Similar attempts to damage Mr Scholz over his links to the Wirecard accounting scandal and the Cum-Ex tax fraud scheme failed to achieve the desired effect.

       Ms Baerbock found herself pushed into a moderator role as the two men got stuck in the minutiae of their past coalition wrangles.

       The candidates represent parties that have governed Germany in a “grand coalition” for 12 out of the past 16 years of Merkel leadership, and face negotiating their way through the formation of another coalition government come September 26 and beyond.

       Mr Scholz declined to rule out coalition talks with far-left party Die Linke, saying that "an acknowledgement of transatlantic relations, Nato and the European Union are necessary for a good government".

       Mr Laschet, in turn, did not rule out the possibility that his party could continue to serve in a coalition with the SPD, but with senior and junior roles reversed in the case of a Scholz victory.

       Ms Baerbock also declined to rule out holding coalition talks between the SPD, the Greens and Die Linke.

       She said Die Linke was “of course a democratic party” that did not represent as extreme positions as the far-right Alternative für Deutschland on the other end of the political spectrum.

       This debate will add to the concern in the CDU camp of what looks set to be an almost certain electoral defeat.

       An opinion poll on Sunday showed that the SPD had extended their lead over the CDU even further.

       The INSA poll put the SPD on 26 percent - up a point from a week ago - and at their highest rating since June 2017.

       The CDU were unchanged at 20 percent and the Greens were down a point at 15 percent.