He has a Doctor of Philosophy from London School of Economics, and was hired at the University of Oslo in 1975.
He was promoted to associate professor in 1980 and professor in 1992. He was the dean of the Faculty of Social Sciences from 2007. Fanny Duckert took over on 1 January 2012.
Heidar edited the journal Scandinavian Political Research from to 1990 to 1993.
His main field of research is political parties and party systems Political parties behind closed doors: Routledge, London 2000.
Norwegian Academy of Science and Letters]
He is a member of the Norwegian Academy of Science and Letters.