The latest public opinion poll, conducted by the organization ZDF Politbarometer last week, confirmed that Merkel's popularity rating had fallen considerably as compared to previous surveys. The figure has dropped to 1.0 from 1.4 on the scale between +5 and —5 since late July, Pletten recalled.
"It is quite possible to perceive it as people's dissatisfaction with [Merkel's] migrant policy with respect to the terrorist attacks that occurred this summer in public places in Germany," she wrote.
She also mentioned another poll carried out by DeutschlandTrend which revealed that only 35 percent of respondents describe Merkel's policy on migrants as satisfactory, the lowest figure since the country's massive influx of asylum seekers began last year.
Merkel's plummeting approval rating, however, has had no negative impact on the voters' support for her Christian Democratic Union party, Pletten said, citing 35 percent of respondents who have repeatedly backed the party, according to polls.
"Also, there are no signs showing that Merkel may not stay on as Chancellor, if she decides to run for new elections next year," Pletten pointed out.
In this vein, she quoted Aftenposten journalist and author of a book about Merkel Ingrid Brekke as saying that "there is no worthy opponent able to get the better of the current German Chancellor."
On July 18, a 17-year-old male youth who had sought asylum in Germany was shot dead by police after wounding five people with an axe on a train near Wuerzburg, also in Bavaria. Police found a hand-painted Daesh (ISIL/ISIS/Islamic State) flag in his flat.
On July 22, an 18-year-old German-Iranian gunman killed nine people in a shopping mall in Munich and injured dozens more in a shoot-out that ended with the gunman shooting himself. According to preliminary data, the shooter adhered to nationalist views and also had mental problems.
On July 24, a 21-year-old Syrian refugee was arrested after killing a pregnant woman and wounding two people with a machete in the southwestern city of Reutlingen, near Stuttgart.
In early July, Bloomberg reported that Merkel's approval rating had risen to its highest point since September 2015 amid her promises to hold the EU together after Britain voted to leave the bloc in June's Brexit referendum.
Bloomberg singled out a poll for ARD television which showed at the time that Merkel's approval rating had increased by nine percentage points to 59 percent.