Jennings was born on a farm in the
Central Valley, California in 1934. He earned his bachelor's degree in Government from the
University of Redlands in 1956 and doctoral degree in Political Science from the
University of North Carolina, Chapel Hill in 1961. After spending three years at the Brookings Institution in 1960–1963, he joined the University of Michigan and was promoted to full professor there in 1969. He was involved in the activities of the Institute for Social Research, the Center for Political Studies, and the Inter-university Consortium for Political and Social Research (ICPSR) at the University of Michigan and was one of the cofounders of ICPSR in 1963. He has been a professor in the Department of Political Science at the University of California, Santa Barbara since 1982. In 1984–1996, he held joint faculty appointment at both the University of California, Santa Barbara and the University of Michigan. He held visiting appointments at institutions such as the
University of Oregon, Tilburg University,
University of California, Los Angeles, and
Arizona State University where he was the first Barry Goldwater Professor of American Institutions. His research has been supported by grants from the National Science Foundation, Russell Sage Foundation, Ford Foundation, National Institute of Mental Health, Army Research Institute, National Institute on Aging, etc. He was a Guggenheim Fellow in 1977–1978, a Fellow at the Center for Advanced Study in the Behavioral Sciences in 1977–1978, and a Fellow at the Netherlands Institute for Advanced Study in the Humanities and Social Sciences in 1989. == Academic work ==