BERLIN — The only televised debate between Chancellor Angela Merkel and her main challenger, Martin Schulz, before German elections later this month appeared not to sway many undecided voters on Sunday about who should be their next leader.
Mrs. Merkel and Mr. Schulz clashed in the 97-minute exchange on refugee policy, Turkey and domestic security. She agreed with his statement that Turkey should not become a member of the European Union, while he expressed doubt about whether President Trump could deal effectively with North Korea’s nuclear provocations.
Polls released by Germany’s public broadcasters afterward declared Mrs. Merkel the winner. But polls also have shown that many voters remain uncertain about who could better lead them over the next four years — and there are three weeks to go before they cast their ballots on Sept. 24.
A survey published last week showed that nearly half of all German voters, 46 percent, remained undecided. Winning their support will be crucial for each candidate.
“Merkel Wins TV Duel,” Bild, the mass-circulation newspaper, said in its digital edition, citing a poll by the public broadcaster ARD that showed 55 percent support for the chancellor, compared with 35 percent for her challenger.
In Freiburg, where a group of residents had been invited to watch the debate, few appeared to be swayed.
Anna Joos told the public broadcaster ZDF that she went in undecided, and saw and heard nothing in the exchange to move her in either direction.
Walter Schneider echoed the lack of conviction about either candidate, telling ZDF, “I don’t see many big differences.”
Another woman, Janina Welke, said: “I think it confirmed many things that I already thought. There was nothing new.”
Germany’s political landscape thrives on consensus, and the two main parties have governed together for four years in a coalition led by Ms. Merkel and her center-right Christian Democratic Union. This was evident in the many instances during the debate that Mr. Schulz, of the center-left Social Democrats, agreed with the chancellor.
For Mr. Schulz, who appeared to capture Germans’ imagination after he announced his candidacy, sending support for his party to highs above 30 percent in February, the debate had largely been viewed as a chance to claw back that position. The Social Democrats have since dropped to around 24 percent.
At the beginning of the debate, he appeared more willing to attack his rival, challenging her decision to throw open Germany’s borders to nearly one million migrants in 2015. It was the start of 45 minutes centered on refugees and integration.
But Mrs. Merkel stood steadfastly by her decision, even as she said a similar action would not happen again.
Germans have a long list of frustrations with Turkey, including the detention of 14 of its citizens on political charges and a vast crackdown by the Turkish government, which has purged around 150,000 public employees, including 4,000 judges and prosecutors.
Mrs. Merkel agreed that Turkey should not become a member of the European bloc, saying that she would seek a joint position on this with other leaders from member nations. Her comments were likely to worsen Germany’s long-running diplomatic feud with Turkey.
Mr. Schulz also targeted Mr. Trump, calling him “unpredictable,” criticizing his habits on Twitter and questioning whether he would be capable of calming the situation over North Korea’s nuclear tests.
But his attacks appeared to give the chancellor the opportunity to play the role for which she is best known at home and abroad: a capable international leader. Mrs. Merkel insisted that despite the difficulties with Turkey, diplomatic relations should not be halted.
The chancellor also said she would do “everything in her power” to keep the United States on a path of diplomacy in dealing with North Korea, even as she made clear that differences with the United States, Germany’s strongest ally, would be called out.
“Merkel played the head of government, who is out and about in the world,” Süddeutsche Zeitung of Munich wrote in an editorial. “Schulz played the friend next door, who would meet viewers at the bar. He was too tame, too stuffy, too conciliatory, too lacking in power-consciousness. He was not a challenger.”