BERLIN (AP) — Angela Merkel's designated successor will quit her role as head of the Germany's strongest party and won't stand for the chancellorship following a debacle in a regional election.

Annegret Kramp-Karrenbauer informed leaders of Merkel's Christian Democratic Union on Monday that she will begin the process of organizing a leadership contest in the summer.

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 the Christian Democrats and the far-right Alternative for Germany back a centrist candidate, breaking what is widely regarded as a taboo around cooperating with extremists in German politics.