BERLIN (AP) — The far-right Alternative for Germany party says it's nominating a member of former Chancellor Angela Merkel’s Christian Democratic Union as its long-shot candidate to become the country’s next president, prompting calls within his own party for him to leave or be expelled.

Max Otte, a right-wing economist who was previously involved with a think-tank close to Alternative for Germany, last year became the head of the Werte-Union — a group that describes itself as representing conservative members of Merkel's center-right Christian Democrats but isn't formally linked to the party. CDU leaders have struggled in recent years to settle on an approach to the Werte-Union, which is politically marginal but has at times gained plenty of attention.

Alternative for Germany, or AfD, on Tuesday announced that Otte was its choice to challenge President Frank-Walter Steinmeier when a special assembly meets Feb. 13 to elect a head of state for the next five years.

Steinmeier has a clear run to a second term because he is backed by most mainstream parties — the three in Chancellor Olaf Scholz's government plus the main opposition Union bloc, which the CDU dominates. Neither Otte nor the Left Party's candidate, medic Gerhard Trabert, has any serious chance in the assembly of the 736 members of the lower house of parliament and an equal number of representatives of Germany's 16 states.

But Otte's nomination is awkward for the CDU as it finds its feet in opposition, and prominent figures said he should leave or be kicked out. Incoming leader Friedrich Merz has strongly ruled out any cooperation with AfD, as did his predecessors.

“Being nominated by AfD as a candidate for the presidency is not an honor but a disgrace,” outgoing leader Armin Laschet wrote on Twitter. “Anyone who even considers this as a Christian Democrat damages the reputation of the Union, violates its values and has no place in the CDU.”

The party's incoming and outgoing general secretaries called on Otte to clarify whether he is accepting the nomination by Tuesday evening and said they may start expulsion proceedings.