BERLIN (Reuters) - Chancellor Angela Merkel’s would-be successor, Annegret Kramp-Karrenbauer, struggled to assert her control over her conservative party on Friday after a regional branch defied her by backing a local leader helped into office by the far right.

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The local branch of Kramp-Karrenbauer’s Christian Democrats (CDU) in the eastern state of Thuringia sided with the far-right Alternative for Germany (AfD) this week in a secret ballot to oust a leftist as state premier.

That move, which saw Thomas Kemmerich of the pro-business FDP become the first state premier to get into power with the support of the AfD, shattered a post-war consensus among established parties to shun the far right.

Merkel and Kramp-Karrenbauer have both denounced the move and say it was taken in defiance of the party’s central leadership.

“The CDU in Thuringia supported this candidate, against the clear recommendation of the federal party ... although it should have been clear to everyone that it was an opportunity for the AfD to play games,” Kramp-Karrenbauer said on Friday.

She also blamed the left for seeking to keep its candidate in power without a majority, and the FDP for putting up its candidate in the first place.

Kramp-Karrenbauer has called for new elections to be held in Thuringia. But the regional branch of the CDU has remained defiant, saying state party leaders had decided it was best to resolve the situation without a new vote. The CDU’s popularity in Thuringia has fallen, making any new election risky.

The party leader’s apparent inability to bring the regional branch to heel drew fire in the German press.

“Annegret Kramp-Karrenbauer, who absolutely wants to become chancellor, has shown that her authority and leadership are not even sufficient to tame the CDU regional chapter in Thuringia,” the conservative Bild newspaper wrote in a commentary.

Lars Klingbeil, secretary general of the Social Democrats, Merkel’s junior coalition party, on Thursday accused the CDU of showing no capacity for crisis management, and suggested Kramp-Karrenbauer knew in advance about the Thuringia plans.

“They deliberately ran into this situation. Thuringia’s CDU accepted this situation, with Kramp-Karrenbauer’s knowledge,” he said.

Kramp-Karrenbauer, 57, won a vote in December 2018 to succeed Merkel as party leader, but has since struggled to impose discipline. Last year she told delegates at a party conference to back her vision for Germany, or else “let’s end it here and now”.

As she struggles to assert herself, Kramp-Karrenbauer’s erstwhile rivals for the party leadership - Friedrich Merz and Jens Spahn - are circling with intent.

Businessman Merz has quit asset manager Blackrock to focus more on politics and Spahn, now health minister, has cut a dynamic figure during the coronavirus crisis, jetting to Paris and London to coordinate the European and G7 response.