BERLIN (AP) — Germany's center-left Social Democrats are electing a new leader to spearhead the party's recovery from a disastrous election result and guide it through a fractious coalition government with Chancellor Angela Merkel's conservatives.

Andrea Nahles, the combative leader of the party's parliamentary group, is overwhelmingly favored to win election at a congress in Wiesbaden on Sunday. But, unusually for Germany, she has a challenger in Simone Lange, the left-leaning mayor of the northern town of Flensburg.

The Social Democrats slumped to their worst result since World War II in September's election, securing only 20.5 percent of the vote. The party initially planned to go into opposition, but reluctantly changed course after Merkel's negotiations with two smaller parties collapsed and eventually agreed to enter another "grand coalition" as the chancellor's junior partner.