A majority of AfD delegates backed the two candidates at a congress in Cologne. The right-wing AfD is seeking to win seats in the national parliament for the first time.
The vote followed a surprise announcement on Wednesday by co-leader Frauke Petry, the party's public face, that she would not lead the AfD's election campaign. This could boost mainstream parties and lessen the threat the right-wing AfD poses to Chancellor Angela Merkel's bid for a fourth term.