On the surface, Ms. Merkel’s two recent trembling episodes within the space of 10 days, which followed a previous incident two years ago in Mexico, have been a strikingly low-key affair in Germany, a country fiercely protective of privacy.

Tight-lipped advisers planted the idea that the second recent episode was psychosomatic, brought on by the memory of the first. The chancellor herself deflected questions in Japan, saying she had “nothing special to report.”

“I am doing fine,” she said.

And that was that.

But under the surface, the images of the chancellor’s moments of physical vulnerability have become symbolic of her party’s and country’s political frailty — and an occasion to revisit the topic of her succession.

In Brussels this week, Ms. Merkel, 64, failed to muster her hallmark consensus-building powers and steer her peers even to her second-choice candidate for the European Union’s top job. Still, in the final hours of negotiations on Tuesday, her influence proved important in getting a German, her defense minister, Ursula von der Leyen, nominated as the president of the powerful European Commission. But domestically, opinion polls now regularly put Ms. Merkel’s conservatives in second place behind the liberal Greens.

Ms. Merkel’s anointed successor, Annegret Kramp-Karrenbauer, who last fall won the contest to succeed the chancellor as head of their conservative party, has seen her approval rating drop sharply in recent weeks as questions about her capacity to lead the party into the next election have grown louder.