He was elected to the Norwegian Parliament from Aust-Agder in 2005. He had previously served as a deputy representative during the terms 1993–1997 and 1997–2001.
On the local level de Ruiter was a member of Arendal city council from 1991 to 1995 and Aust-Agder county council from 1995 to 2007. He chairs the local party chapter since 2004.