In her capacity as secretary general, Nahles oversaw the SPD's electoral campaign in 2013. After the SPD's defeat in the federal elections, she was in charge of organizing a referendum among her party's 472,000 members before signing any coalition treaty with re-elected Chancellor Angela Merkel and her conservative bloc. In the negotiations to form a coalition government following the elections, Nahles was part of the 15-member leadership circle chaired by Merkel, Gabriel and Horst Seehofer.