Christensen was a lawyer and military officer, and was appointed governor of the County of Northern Bergenhus in 1910 and held the position until 1929 (in 1918 the county was renamed Sogn og Fjordane). He was subsequently county governor of Oslo and Akershus from 1929 to 1941.
After the German invasion of Norway in 1940 was he elected Chairman of the new Administrative Council that was put up by the Norwegian Supreme Court and functioned from April to September 1940. The council held negotiations with the Germans and Christensen was regarded by the Germans as a possible leader of a suggested Riksråd that should govern Norway. The negotiations however failed and came to an end in September 1940. He then returned to his office as county governor until 1941 when he was replaced by a member of Nasjonal Samling. After that he withdrew to his family farm and did not play a political role any longer.