 He was elected Chairman of the Independence Party in an uncontested election in October 2005, following the departure of Davíð Oddsson.Following the announcement of Halldór Ásgrímsson's resignation as Prime Minister on 5 June 2006, Geir succeeded him as Prime Minister on 15 June.On 23 January 2009, Geir announced that due to health reasons (malignant oesophageal tumour), he would step down as chairman of the Independence Party at the next party congress on 26–29 March 2009.