Napthine was a Liberal Party member of the Victorian Legislative Assembly, representing the electoral district of Portland from 1988 to 2002 and South-West Coast from 2002 to 2015. He was elected leader of the Parliamentary Liberal Party on 6 March 2013 following the resignation of Ted Baillieu and was sworn in as premier on the same day. His party lost the Victorian state election on 29 November 2014 and he announced he would step down as leader of the Parliamentary Liberal Party, with Matthew Guy being elected his successor on 4 December.