Ahead of the Christian Democrats’ leadership election in 2018, Schummer publicly endorsed Annegret Kramp-Karrenbauer to succeed Angela Merkel as the party’s chair. In 2019, he joined 14 members of his parliamentary group who, in an open letter, called for the party to rally around Merkel and Kramp-Karrenbauer amid criticism voiced by conservatives Friedrich Merz and Roland Koch.