(CNN) Angela Merkel's grand transition plan has derailed after her handpicked successor, Annegret Kramp-Karrenbauer, unexpectedly called it quits on Monday.

Kramp-Karrenbauer, better known as AKK, announced she would not stand as the Christian Democratic Union's (CDU) candidate to be German chancellor in the next federal election. She is also stepping down as the party's chairwoman, according to the CDU's press office.

Merkel, who has been chancellor for almost 15 years, said in 2018 that she would not run again when her term expires in 2021. At that time, she stepped down as party leader and endorsed Kramp-Karrenbauer as her successor. But her attempt at securing an orderly transition of power -- as well as her own legacy -- appears to have failed.

Some say the chaos is of Merkel's own making.

"To me, this failure is symptomatic of the way Angela Merkel has exercised power," said Henrik Enderlein, president of the Hertie School of Governance in Berlin. "She never allowed anyone to rise within the federal government and become a natural heir."

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