Jenssen was a local politician in Trondheim for a long time and served as political adviser to mayor Marvin Wiseth.[1] He was State Secretary for Erna Solberg in the Ministry of Local Government and Regional Development from 2003 to 2005. He was the Conservative Party's candidate for mayor in Trondheim in the municipalities elections in 2003 and 2007, but the Labour Party with Rita Ottervik got the position of mayor both times.[2]