Hart returned to private practice after the 1988 election and served in a variety of public roles. He co-chaired the Hart-Rudman Task Force on Homeland Security, served on the Homeland Security Advisory Council, and was the United States Special Envoy for Northern Ireland. He earned a doctorate in politics from the University of Oxford and has written for outlets such as "The Huffington Post". He has also written several books, including a biography of President James Monroe. Hart has been married to Lee (Ludwig) since 1958 and has two children.