BERLIN (AP) German Chancellor Angela Merkel s designated successor will quit her role as head of Germanys strongest party and wont stand for the chancellorship following a debacle in a regional election.

Annegret Kramp-Karrenbauer informed leading members of Merkels conservative Christian Democratic Union on Monday that she will begin the process of organizing a leadership contest in the summer. Germany is scheduled to hold its next general election in the fall of 2021 and Merkel, who has led Germany for 15 years, has said she will not run for a fifth term as chancellor.

The move comes days after her party was heavily criticized for its handling of a vote for governor in the eastern state of Thuringia that saw both the Christian Democrats and the far-right Alternative for Germany party back a centrist candidate. The move broke what is widely regarded as a taboo around cooperating with extremists in German politics.

Kramp-Karrenbauer, often referred to by the acronym AKK, took over the leadership of the Christian Democrats in December 2018 after beating out Health Minister Jens Spahn and Friedrich Merz, a former party veteran sidelined by Merkel before she became chancellor in 2005.

Kramp-Karrenbauer, who is also Germanys defense minister, struggled to boost the partys declining election results amid a stiff challenge from the far-right.

The fiasco in Thuringia state further highlighted tensions in the center-right Christian Democrats after the partys regional lawmakers ignored a recommendation from Berlin not to back a centrist candidate against the left-wing incumbent.