Olaf Scholz, the Social Democrat candidate running to become Germany’s new leader, has promised “moderate” solutions to fight climate change.
Mr Scholz, the country's current Vice Chancellor, topped opinion polls after a TV showdown at the weekend in which he clashed with the Christian Democrat candidate Armin Laschet and the Greens’ Annalena Baerbock on a wide range of issues.
The debate, described in the German media as “aggressive”, came just two weeks before voters will go to the polls.
Mr Scholz said that if he becomes chancellor, Germans would not be faced with too much rapid change when it comes to climate change policies.
“I have always resisted those who have said that everything must now quickly become much more expensive,” he said.
This was regarded as a thinly veiled attack on Ms Baerbock. Over the years, the Greens have been accused of changing into a party of bans.
“We want to go a moderate way," Mr Scholz said. "It’s the right thing to do.”
Ms Baerbock said that a move towards more climate-friendly initiatives needed to happen fast.
She pushed for the 2035 EU target to phase out sales of petrol and diesel cars to be brought forward.
The proposal is likely to cause unease among Germany's manufacturing industry.
Mr Laschet and Ms Baerbock, the two candidates who face the most pressure, gave combative performances but remained polite throughout.
Ms Baerbock called for a ban on combustion-engine vehicles by 2030 and a rapid switch to electric cars.
“We need to get out of the combustion engine, fossil fuels,” she said.
Ms Baerbock then turned her focus to Mr Laschet, saying: “You always say you don’t like bans but it’s always a driver for innovation.”
Mr Laschet insisted his party was taking the battle against climate change seriously.
"The German auto industry is long since on the path to adjusting,” he said.
He went on to accuse Mr Scholz and Ms Baerbock of trying to hamstring industries, saying: "It won't work with laws, with bans, with regulations, but with a dynamic where everyone is keen to create something new."
A snap poll conducted after the debate showed that Mr Scholz repeated the clear victory he earned in the first debate, with 41 per cent of viewers describing him as the most convincing.
Mr Laschet won 27 per cent of the vote ahead of Ms Baerbock on 25 per cent.
On September 26, after a third and final debate, Germans will elect a new Bundestag, or federal parliament, and the fight for the top spot is heating up.
Coalition negotiations after the debate are likely to involve two or three parties and will decide who will be the successor of Angela Merkel, who is standing down after 16 years.
In recent weeks, poll after poll have shown Mr Scholz’s party on the rise while the CDU and the Greens lag behind.
The security situation in Afghanistan was also discussed by the three candidates, weeks after the German government scrambled to get its citizens and vulnerable Afghans out of Kabul.
German troops had earlier withdrawn from the country, along with the US and other allies.
Mr Laschet called the Taliban’s return to power “a disaster for the West, also a disaster for the German government”. He said it was time to create a national security council to improve decision-making in Germany.
Ms Baerbock accused the government of “ducking away” from decisions on rescuing Afghans.
Mr Scholz pointed to the government’s efforts to help Afghans leave the country after they missed evacuation flights.
The city of Potsdam, on the outskirts of Berlin, has become an arena for the battle to succeed Mrs Merkel.
Ms Baerbock and Mr Scholz are both running in constituency 61, which includes Potsdam.
The battle marks the first time in German history that two chancellor candidates have gone head-to-head in the same constituency – a far cry from the "safe seat" route often favoured by past political heavyweights.
Because seats in the Bundestag are filled through a combination of direct mandates and party lists, both Mr Scholz and Ms Baerbock could still become MPs even if they lose in Potsdam.
However, winning a direct mandate would be the icing on the cake.
Karl-Rudolf Korte, a professor of politics at the University of Duisburg-Essen, told AFP: "Constituency kings and queens have a special legitimacy in the Bundestag.
"Both candidates have their place secured via the list. Nevertheless, the competition is more than just symbolic."