He was elected to the Norwegian Parliament from Akershus in 1993, and was re-elected on three occasions. He had previously served as a deputy representative during the term 1989–1993. From 1989 to 1990 he moved up as a regular representative, filling in for Kaci Kullmann Five who was appointed to the cabinet Syse.
In the Norwegian Young Conservatives, the youth wing of the Conservative Party, he chaired the local chapter from 1985 to 1986, the regional chapter from 1987 to 1988, became deputy leader nationwide in 1988 and leader from 1990 to 1994. In the Conservative Party he was a member of the central party board from 1988 to 1994, served as first deputy leader of the regional branch from 2001 to 2005. He was second deputy leader of the nationwide party from 2004 to 2008, and rose to first deputy leader in 2008.
As a result of the parliamentary election in the fall of 2013, Sanner holds the position as Minister of Local Government and Modernisation in the coalition government led by Prime Minister Erna Solberg.